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	$54.82	11.302%	$61.0158	$61.02	$61.00	$61.00
Purchase #2	$33.36	11.196%	$37.095	$37.10	$37.10	$37.10
Purchase #3	$88.84	7.237%	$95.2694	$95.27	$95.25	$95.30
Purchase #4	$61.40	10.113%	$67.6094	$67.61	$67.60	$67.60
Purchase #5	$82.30	5.530%	$86.8512	$86.85	$86.85	$86.90
Purchase #6	$188.40	7.310%	$202.172	$202.17	$202.15	$202.20
Purchase #7	$240.47	3.164%	$248.0785	$248.08	$248.10	$248.10
7 purchase totals =	$749.59		$798.0913	$798.10	$798.05	$798.20