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	$80.59	8.173%	$87.1766	$87.18	$87.20	$87.20
Purchase #2	$199.78	3.447%	$206.6664	$206.67	$206.65	$206.70
Purchase #3	$240.98	11.120%	$267.777	$267.78	$267.80	$267.80
Purchase #4	$148.54	11.394%	$165.4646	$165.46	$165.45	$165.50
Purchase #5	$35.70	13.819%	$40.6334	$40.63	$40.65	$40.60
Purchase #6	$66.62	9.417%	$72.8936	$72.89	$72.90	$72.90
Purchase #7	$248.48	3.405%	$256.9407	$256.94	$256.95	$256.90
7 purchase totals =	$1,020.69		$1,097.5523	$1,097.55	$1,097.60	$1,097.60