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	$29.31	11.722%	$32.7457	$32.75	$32.75	$32.70
Purchase #2	$204.25	9.746%	$224.1562	$224.16	$224.15	$224.20
Purchase #3	$159.69	5.864%	$169.0542	$169.05	$169.05	$169.10
Purchase #4	$98.35	4.354%	$102.6322	$102.63	$102.65	$102.60
Purchase #5	$95.61	4.823%	$100.2213	$100.22	$100.20	$100.20
Purchase #6	$72.91	9.494%	$79.8321	$79.83	$79.85	$79.80
Purchase #7	$42.49	3.154%	$43.8301	$43.83	$43.85	$43.80
7 purchase totals =	$702.61		$752.4718	$752.47	$752.50	$752.40