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	$90.71	8.721%	$98.6208	$98.62	$98.60	$98.60
Purchase #2	$39.34	11.216%	$43.7524	$43.75	$43.75	$43.80
Purchase #3	$91.54	9.279%	$100.034	$100.03	$100.05	$100.00
Purchase #4	$108.52	12.324%	$121.894	$121.89	$121.90	$121.90
Purchase #5	$132.67	3.713%	$137.596	$137.60	$137.60	$137.60
Purchase #6	$105.25	5.566%	$111.1082	$111.11	$111.10	$111.10
Purchase #7	$196.31	8.605%	$213.2025	$213.20	$213.20	$213.20
7 purchase totals =	$764.34		$826.2079	$826.20	$826.20	$826.20