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	$50.58	6.868%	$54.0538	$54.05	$54.05	$54.10
Purchase #2	$43.31	3.350%	$44.7609	$44.76	$44.75	$44.80
Purchase #3	$126.81	12.378%	$142.5065	$142.51	$142.50	$142.50
Purchase #4	$143.79	13.243%	$162.8321	$162.83	$162.85	$162.80
Purchase #5	$27.53	13.846%	$31.3418	$31.34	$31.35	$31.30
Purchase #6	$11.38	4.802%	$11.9265	$11.93	$11.95	$11.90
Purchase #7	$17.50	12.816%	$19.7428	$19.74	$19.75	$19.70
7 purchase totals =	$420.90		$467.1644	$467.16	$467.20	$467.10