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	$43.69	4.724%	$45.7539	$45.75	$45.75	$45.80
Purchase #2	$75.64	10.390%	$83.499	$83.50	$83.50	$83.50
Purchase #3	$231.66	10.224%	$255.3449	$255.34	$255.35	$255.30
Purchase #4	$155.85	4.529%	$162.9084	$162.91	$162.90	$162.90
Purchase #5	$87.62	6.836%	$93.6097	$93.61	$93.60	$93.60
Purchase #6	$113.82	6.846%	$121.6121	$121.61	$121.60	$121.60
Purchase #7	$144.50	12.282%	$162.2475	$162.25	$162.25	$162.20
7 purchase totals =	$852.78		$924.9755	$924.97	$924.95	$924.90