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	$48.64	9.111%	$53.0716	$53.07	$53.05	$53.10
Purchase #2	$56.42	4.299%	$58.8455	$58.85	$58.85	$58.80
Purchase #3	$153.36	3.512%	$158.746	$158.75	$158.75	$158.70
Purchase #4	$155.56	5.675%	$164.388	$164.39	$164.40	$164.40
Purchase #5	$85.84	5.819%	$90.835	$90.84	$90.85	$90.80
Purchase #6	$209.38	7.231%	$224.5203	$224.52	$224.50	$224.50
Purchase #7	$16.53	3.816%	$17.1608	$17.16	$17.15	$17.20
7 purchase totals =	$725.73		$767.5672	$767.58	$767.55	$767.50