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	$51.82	6.459%	$55.1671	$55.17	$55.15	$55.20
Purchase #2	$216.49	13.221%	$245.1121	$245.11	$245.10	$245.10
Purchase #3	$233.86	4.700%	$244.8514	$244.85	$244.85	$244.90
Purchase #4	$7.54	3.874%	$7.8321	$7.83	$7.85	$7.80
Purchase #5	$32.64	13.570%	$37.0692	$37.07	$37.05	$37.10
Purchase #6	$201.47	13.746%	$229.1641	$229.16	$229.15	$229.20
Purchase #7	$80.76	3.385%	$83.4937	$83.49	$83.50	$83.50
7 purchase totals =	$824.58		$902.6897	$902.68	$902.65	$902.80