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	$124.41	4.707%	$130.266	$130.27	$130.25	$130.30
Purchase #2	$119.51	10.281%	$131.7968	$131.80	$131.80	$131.80
Purchase #3	$34.37	13.161%	$38.8934	$38.89	$38.90	$38.90
Purchase #4	$94.32	12.181%	$105.8091	$105.81	$105.80	$105.80
Purchase #5	$106.97	6.198%	$113.6	$113.60	$113.60	$113.60
Purchase #6	$248.85	8.555%	$270.1391	$270.14	$270.15	$270.10
Purchase #7	$144.32	6.637%	$153.8985	$153.90	$153.90	$153.90
7 purchase totals =	$872.75		$944.4029	$944.41	$944.40	$944.40