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	$186.55	7.663%	$200.8453	$200.85	$200.85	$200.80
Purchase #2	$209.71	13.610%	$238.2515	$238.25	$238.25	$238.30
Purchase #3	$198.48	11.447%	$221.2	$221.20	$221.20	$221.20
Purchase #4	$127.98	10.734%	$141.7174	$141.72	$141.70	$141.70
Purchase #5	$54.64	7.251%	$58.6019	$58.60	$58.60	$58.60
Purchase #6	$86.39	3.181%	$89.1381	$89.14	$89.15	$89.10
Purchase #7	$19.32	7.543%	$20.7773	$20.78	$20.80	$20.80
7 purchase totals =	$883.07		$970.5315	$970.54	$970.55	$970.50