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	$134.79	11.381%	$150.1304	$150.13	$150.15	$150.10
Purchase #2	$37.98	6.793%	$40.56	$40.56	$40.55	$40.60
Purchase #3	$99.33	12.658%	$111.9032	$111.90	$111.90	$111.90
Purchase #4	$45.71	8.221%	$49.4678	$49.47	$49.45	$49.50
Purchase #5	$94.41	12.702%	$106.402	$106.40	$106.40	$106.40
Purchase #6	$10.88	5.833%	$11.5146	$11.51	$11.50	$11.50
Purchase #7	$48.54	13.282%	$54.9871	$54.99	$55.00	$55.00
7 purchase totals =	$471.64		$524.9651	$524.96	$524.95	$525.00