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	$90.91	7.496%	$97.7246	$97.72	$97.70	$97.70
Purchase #2	$136.36	12.447%	$153.3327	$153.33	$153.35	$153.30
Purchase #3	$153.71	4.578%	$160.7468	$160.75	$160.75	$160.70
Purchase #4	$166.28	7.749%	$179.165	$179.17	$179.15	$179.20
Purchase #5	$97.29	8.412%	$105.474	$105.47	$105.45	$105.50
Purchase #6	$44.89	3.836%	$46.612	$46.61	$46.60	$46.60
Purchase #7	$213.29	4.340%	$222.5468	$222.55	$222.55	$222.50
7 purchase totals =	$902.73		$965.6019	$965.60	$965.55	$965.50