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	$47.86	13.262%	$54.2072	$54.21	$54.20	$54.20
Purchase #2	$196.65	6.847%	$210.1146	$210.11	$210.10	$210.10
Purchase #3	$6.31	6.476%	$6.7186	$6.72	$6.70	$6.70
Purchase #4	$28.77	13.123%	$32.5455	$32.55	$32.55	$32.50
Purchase #5	$84.90	5.576%	$89.634	$89.63	$89.65	$89.60
Purchase #6	$144.49	5.867%	$152.9672	$152.97	$152.95	$153.00
Purchase #7	$174.54	11.653%	$194.8791	$194.88	$194.90	$194.90
7 purchase totals =	$683.52		$741.0662	$741.07	$741.05	$741.00