Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$148.90	10.447%	$164.4556	$164.46	$164.45	$164.50
Purchase #2	$151.52	8.521%	$164.431	$164.43	$164.45	$164.40
Purchase #3	$99.25	6.676%	$105.8759	$105.88	$105.90	$105.90
Purchase #4	$102.50	10.482%	$113.2441	$113.24	$113.25	$113.20
Purchase #5	$231.59	13.497%	$262.8477	$262.85	$262.85	$262.80
Purchase #6	$203.37	4.721%	$212.9711	$212.97	$212.95	$213.00
Purchase #7	$174.75	6.142%	$185.4831	$185.48	$185.50	$185.50
7 purchase totals =	$1,111.88		$1,209.3085	$1,209.31	$1,209.35	$1,209.30