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	$203.54	9.524%	$222.9251	$222.93	$222.95	$222.90
Purchase #2	$129.46	13.253%	$146.6173	$146.62	$146.60	$146.60
Purchase #3	$197.71	7.140%	$211.8265	$211.83	$211.85	$211.80
Purchase #4	$26.66	6.770%	$28.4649	$28.46	$28.45	$28.50
Purchase #5	$20.96	3.634%	$21.7217	$21.72	$21.70	$21.70
Purchase #6	$18.43	11.149%	$20.4848	$20.48	$20.50	$20.50
Purchase #7	$46.57	12.759%	$52.5119	$52.51	$52.50	$52.50
7 purchase totals =	$643.33		$704.5522	$704.55	$704.55	$704.50