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	$174.96	9.698%	$191.9276	$191.93	$191.95	$191.90
Purchase #2	$82.70	10.767%	$91.6043	$91.60	$91.60	$91.60
Purchase #3	$241.98	13.702%	$275.1361	$275.14	$275.15	$275.10
Purchase #4	$13.39	5.311%	$14.1011	$14.10	$14.10	$14.10
Purchase #5	$80.83	12.620%	$91.0307	$91.03	$91.05	$91.00
Purchase #6	$115.25	11.521%	$128.528	$128.53	$128.55	$128.50
Purchase #7	$26.83	4.472%	$28.0298	$28.03	$28.05	$28.00
7 purchase totals =	$735.94		$820.3576	$820.36	$820.45	$820.20