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	$160.93	8.789%	$175.0741	$175.07	$175.05	$175.10
Purchase #2	$38.41	5.731%	$40.6113	$40.61	$40.60	$40.60
Purchase #3	$226.42	8.188%	$244.9593	$244.96	$244.95	$245.00
Purchase #4	$81.25	11.626%	$90.6961	$90.70	$90.70	$90.70
Purchase #5	$59.72	4.554%	$62.4396	$62.44	$62.45	$62.40
Purchase #6	$98.85	5.746%	$104.5299	$104.53	$104.55	$104.50
Purchase #7	$194.61	11.211%	$216.4277	$216.43	$216.45	$216.40
7 purchase totals =	$860.19		$934.7380	$934.74	$934.75	$934.70