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	$229.89	8.405%	$249.2123	$249.21	$249.20	$249.20
Purchase #2	$155.56	5.605%	$164.2791	$164.28	$164.30	$164.30
Purchase #3	$178.40	7.426%	$191.648	$191.65	$191.65	$191.60
Purchase #4	$224.48	3.308%	$231.9058	$231.91	$231.90	$231.90
Purchase #5	$18.49	10.824%	$20.4914	$20.49	$20.50	$20.50
Purchase #6	$123.37	10.438%	$136.2474	$136.25	$136.25	$136.20
Purchase #7	$75.47	3.822%	$78.3545	$78.35	$78.35	$78.40
7 purchase totals =	$1,005.66		$1,072.1385	$1,072.14	$1,072.15	$1,072.10