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	$223.70	4.558%	$233.8962	$233.90	$233.90	$233.90
Purchase #2	$47.75	13.523%	$54.2072	$54.21	$54.20	$54.20
Purchase #3	$64.28	6.388%	$68.3862	$68.39	$68.40	$68.40
Purchase #4	$48.62	10.832%	$53.8865	$53.89	$53.90	$53.90
Purchase #5	$15.53	13.112%	$17.5663	$17.57	$17.55	$17.60
Purchase #6	$168.25	6.450%	$179.1021	$179.10	$179.10	$179.10
Purchase #7	$171.26	8.130%	$185.1834	$185.18	$185.20	$185.20
7 purchase totals =	$739.39		$792.2279	$792.24	$792.25	$792.30