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	$85.96	6.383%	$91.4468	$91.45	$91.45	$91.40
Purchase #2	$63.53	6.275%	$67.5165	$67.52	$67.50	$67.50
Purchase #3	$213.43	4.145%	$222.2767	$222.28	$222.30	$222.30
Purchase #4	$223.81	13.194%	$253.3395	$253.34	$253.35	$253.30
Purchase #5	$180.34	5.273%	$189.8493	$189.85	$189.85	$189.80
Purchase #6	$33.88	7.547%	$36.4369	$36.44	$36.45	$36.40
Purchase #7	$186.77	7.377%	$200.548	$200.55	$200.55	$200.50
7 purchase totals =	$987.72		$1,061.4137	$1,061.43	$1,061.45	$1,061.20