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	$182.44	4.454%	$190.5659	$190.57	$190.55	$190.60
Purchase #2	$55.99	11.575%	$62.4708	$62.47	$62.45	$62.50
Purchase #3	$153.62	4.760%	$160.9323	$160.93	$160.95	$160.90
Purchase #4	$209.97	6.138%	$222.858	$222.86	$222.85	$222.90
Purchase #5	$221.75	5.301%	$233.505	$233.51	$233.50	$233.50
Purchase #6	$47.85	5.174%	$50.3258	$50.33	$50.35	$50.30
Purchase #7	$243.43	10.818%	$269.7643	$269.76	$269.75	$269.80
7 purchase totals =	$1,115.05		$1,190.4221	$1,190.43	$1,190.40	$1,190.50