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	$220.90	4.637%	$231.1431	$231.14	$231.15	$231.10
Purchase #2	$209.38	4.476%	$218.7518	$218.75	$218.75	$218.80
Purchase #3	$180.44	13.131%	$204.1336	$204.13	$204.15	$204.10
Purchase #4	$79.85	12.213%	$89.6021	$89.60	$89.60	$89.60
Purchase #5	$137.63	7.622%	$148.1202	$148.12	$148.10	$148.10
Purchase #6	$124.95	5.225%	$131.4786	$131.48	$131.50	$131.50
Purchase #7	$92.48	4.795%	$96.9144	$96.91	$96.90	$96.90
7 purchase totals =	$1,045.63		$1,120.1438	$1,120.13	$1,120.15	$1,120.10