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	$83.93	7.863%	$90.5294	$90.53	$90.55	$90.50
Purchase #2	$59.63	3.753%	$61.8679	$61.87	$61.85	$61.90
Purchase #3	$174.66	9.754%	$191.6963	$191.70	$191.70	$191.70
Purchase #4	$95.40	7.846%	$102.8851	$102.89	$102.90	$102.90
Purchase #5	$181.49	11.251%	$201.9094	$201.91	$201.90	$201.90
Purchase #6	$95.50	10.503%	$105.5304	$105.53	$105.55	$105.50
Purchase #7	$195.42	6.819%	$208.7457	$208.75	$208.75	$208.70
7 purchase totals =	$886.03		$963.1642	$963.18	$963.20	$963.10