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	$240.58	5.770%	$254.4615	$254.46	$254.45	$254.50
Purchase #2	$45.32	7.263%	$48.6116	$48.61	$48.60	$48.60
Purchase #3	$150.81	3.531%	$156.1351	$156.14	$156.15	$156.10
Purchase #4	$215.49	3.846%	$223.7777	$223.78	$223.80	$223.80
Purchase #5	$201.44	3.494%	$208.4783	$208.48	$208.50	$208.50
Purchase #6	$200.63	4.353%	$209.3634	$209.36	$209.35	$209.40
Purchase #7	$65.67	9.177%	$71.6965	$71.70	$71.70	$71.70
7 purchase totals =	$1,119.94		$1,172.5241	$1,172.53	$1,172.55	$1,172.60