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	$124.27	3.152%	$128.187	$128.19	$128.20	$128.20
Purchase #2	$52.44	9.788%	$57.5728	$57.57	$57.55	$57.60
Purchase #3	$49.32	8.404%	$53.4649	$53.46	$53.45	$53.50
Purchase #4	$130.79	5.121%	$137.4878	$137.49	$137.50	$137.50
Purchase #5	$85.96	9.504%	$94.1296	$94.13	$94.15	$94.10
Purchase #6	$55.31	5.714%	$58.4704	$58.47	$58.45	$58.50
Purchase #7	$240.84	7.191%	$258.1588	$258.16	$258.15	$258.20
7 purchase totals =	$738.93		$787.4713	$787.47	$787.45	$787.60