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	$39.89	13.743%	$45.3721	$45.37	$45.35	$45.40
Purchase #2	$44.25	7.869%	$47.732	$47.73	$47.75	$47.70
Purchase #3	$124.90	13.864%	$142.2161	$142.22	$142.20	$142.20
Purchase #4	$126.62	8.114%	$136.8939	$136.89	$136.90	$136.90
Purchase #5	$14.89	6.719%	$15.8905	$15.89	$15.90	$15.90
Purchase #6	$173.78	9.210%	$189.7851	$189.79	$189.80	$189.80
Purchase #7	$237.31	13.629%	$269.653	$269.65	$269.65	$269.70
7 purchase totals =	$761.64		$847.5427	$847.54	$847.55	$847.60