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	$121.31	5.470%	$127.9457	$127.95	$127.95	$127.90
Purchase #2	$105.51	9.811%	$115.8616	$115.86	$115.85	$115.90
Purchase #3	$45.82	11.393%	$51.0403	$51.04	$51.05	$51.00
Purchase #4	$130.35	4.820%	$136.6329	$136.63	$136.65	$136.60
Purchase #5	$137.48	8.747%	$149.5054	$149.51	$149.50	$149.50
Purchase #6	$137.93	4.320%	$143.8886	$143.89	$143.90	$143.90
Purchase #7	$24.33	13.305%	$27.5671	$27.57	$27.55	$27.60
7 purchase totals =	$702.73		$752.4416	$752.45	$752.45	$752.40