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	$179.55	13.310%	$203.4481	$203.45	$203.45	$203.40
Purchase #2	$246.26	7.585%	$264.9388	$264.94	$264.95	$264.90
Purchase #3	$144.64	7.427%	$155.3824	$155.38	$155.40	$155.40
Purchase #4	$65.31	12.667%	$73.5828	$73.58	$73.60	$73.60
Purchase #5	$95.94	4.127%	$99.8994	$99.90	$99.90	$99.90
Purchase #6	$222.99	9.728%	$244.6825	$244.68	$244.70	$244.70
Purchase #7	$152.78	3.640%	$158.3412	$158.34	$158.35	$158.30
7 purchase totals =	$1,107.47		$1,200.2752	$1,200.27	$1,200.35	$1,200.20