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	$61.54	13.320%	$69.7371	$69.74	$69.75	$69.70
Purchase #2	$37.33	7.806%	$40.244	$40.24	$40.25	$40.20
Purchase #3	$84.84	9.872%	$93.2154	$93.22	$93.20	$93.20
Purchase #4	$159.41	13.798%	$181.4054	$181.41	$181.40	$181.40
Purchase #5	$203.77	9.646%	$223.4257	$223.43	$223.45	$223.40
Purchase #6	$247.77	12.274%	$278.1813	$278.18	$278.20	$278.20
Purchase #7	$216.48	4.219%	$225.6133	$225.61	$225.60	$225.60
7 purchase totals =	$1,011.14		$1,111.8222	$1,111.83	$1,111.85	$1,111.70