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	$118.51	5.117%	$124.5742	$124.57	$124.55	$124.60
Purchase #2	$12.50	3.718%	$12.9648	$12.96	$12.95	$13.00
Purchase #3	$99.49	12.213%	$111.6407	$111.64	$111.65	$111.60
Purchase #4	$44.47	5.238%	$46.7993	$46.80	$46.80	$46.80
Purchase #5	$53.70	9.872%	$59.0013	$59.00	$59.00	$59.00
Purchase #6	$93.53	5.558%	$98.7284	$98.73	$98.75	$98.70
Purchase #7	$118.70	4.433%	$123.962	$123.96	$123.95	$124.00
7 purchase totals =	$540.90		$577.6707	$577.66	$577.65	$577.70