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	$96.63	3.840%	$100.3406	$100.34	$100.35	$100.30
Purchase #2	$240.72	6.401%	$256.1285	$256.13	$256.15	$256.10
Purchase #3	$169.33	13.557%	$192.2861	$192.29	$192.30	$192.30
Purchase #4	$140.81	4.865%	$147.6604	$147.66	$147.65	$147.70
Purchase #5	$88.92	8.131%	$96.1501	$96.15	$96.15	$96.20
Purchase #6	$249.61	5.334%	$262.9242	$262.92	$262.90	$262.90
Purchase #7	$130.81	8.208%	$141.5469	$141.55	$141.55	$141.50
7 purchase totals =	$1,116.83		$1,197.0368	$1,197.04	$1,197.05	$1,197.00