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	$118.75	7.567%	$127.7358	$127.74	$127.75	$127.70
Purchase #2	$23.94	9.111%	$26.1212	$26.12	$26.10	$26.10
Purchase #3	$69.58	3.337%	$71.9019	$71.90	$71.90	$71.90
Purchase #4	$208.38	8.672%	$226.4507	$226.45	$226.45	$226.50
Purchase #5	$113.82	5.387%	$119.9515	$119.95	$119.95	$120.00
Purchase #6	$135.47	8.144%	$146.5027	$146.50	$146.50	$146.50
Purchase #7	$105.31	5.831%	$111.4506	$111.45	$111.45	$111.50
7 purchase totals =	$775.25		$830.1144	$830.11	$830.10	$830.20