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	$179.91	4.762%	$188.4773	$188.48	$188.50	$188.50
Purchase #2	$166.68	13.222%	$188.7184	$188.72	$188.70	$188.70
Purchase #3	$233.58	4.348%	$243.7361	$243.74	$243.75	$243.70
Purchase #4	$90.62	10.275%	$99.9312	$99.93	$99.95	$99.90
Purchase #5	$194.50	7.728%	$209.531	$209.53	$209.55	$209.50
Purchase #6	$145.27	4.692%	$152.0861	$152.09	$152.10	$152.10
Purchase #7	$159.31	8.650%	$173.0903	$173.09	$173.10	$173.10
7 purchase totals =	$1,169.87		$1,255.5704	$1,255.58	$1,255.65	$1,255.50