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	$52.57	6.160%	$55.8083	$55.81	$55.80	$55.80
Purchase #2	$26.91	4.398%	$28.0935	$28.09	$28.10	$28.10
Purchase #3	$69.98	4.152%	$72.8856	$72.89	$72.90	$72.90
Purchase #4	$97.69	13.832%	$111.2025	$111.20	$111.20	$111.20
Purchase #5	$162.96	7.870%	$175.785	$175.79	$175.80	$175.80
Purchase #6	$36.32	13.507%	$41.2257	$41.23	$41.25	$41.20
Purchase #7	$118.35	7.425%	$127.1375	$127.14	$127.15	$127.10
7 purchase totals =	$564.78		$612.1381	$612.15	$612.20	$612.10