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	$240.30	3.106%	$247.7637	$247.76	$247.75	$247.80
Purchase #2	$116.31	12.183%	$130.48	$130.48	$130.50	$130.50
Purchase #3	$7.62	3.785%	$7.9084	$7.91	$7.90	$7.90
Purchase #4	$78.54	10.444%	$86.7427	$86.74	$86.75	$86.70
Purchase #5	$97.96	8.547%	$106.3326	$106.33	$106.35	$106.30
Purchase #6	$173.25	13.478%	$196.6006	$196.60	$196.60	$196.60
Purchase #7	$190.82	4.513%	$199.4317	$199.43	$199.45	$199.40
7 purchase totals =	$904.80		$975.2597	$975.25	$975.30	$975.20