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	$72.47	5.348%	$76.3457	$76.35	$76.35	$76.30
Purchase #2	$147.84	11.435%	$164.7455	$164.75	$164.75	$164.70
Purchase #3	$135.27	7.646%	$145.6127	$145.61	$145.60	$145.60
Purchase #4	$99.37	9.456%	$108.7664	$108.77	$108.75	$108.80
Purchase #5	$223.76	10.440%	$247.1205	$247.12	$247.10	$247.10
Purchase #6	$93.98	5.389%	$99.0446	$99.04	$99.05	$99.00
Purchase #7	$249.56	10.427%	$275.5816	$275.58	$275.60	$275.60
7 purchase totals =	$1,022.25		$1,117.2170	$1,117.22	$1,117.20	$1,117.10