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	$224.52	12.758%	$253.1643	$253.16	$253.15	$253.20
Purchase #2	$249.85	13.335%	$283.1675	$283.17	$283.15	$283.20
Purchase #3	$53.58	11.806%	$59.9057	$59.91	$59.90	$59.90
Purchase #4	$89.84	9.695%	$98.55	$98.55	$98.55	$98.60
Purchase #5	$244.37	5.705%	$258.3113	$258.31	$258.30	$258.30
Purchase #6	$26.28	9.179%	$28.6922	$28.69	$28.70	$28.70
Purchase #7	$76.84	11.506%	$85.6812	$85.68	$85.70	$85.70
7 purchase totals =	$965.28		$1,067.4722	$1,067.47	$1,067.45	$1,067.60