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	$67.43	13.515%	$76.5432	$76.54	$76.55	$76.50
Purchase #2	$182.62	3.182%	$188.431	$188.43	$188.45	$188.40
Purchase #3	$57.35	3.834%	$59.5488	$59.55	$59.55	$59.50
Purchase #4	$18.95	11.610%	$21.1501	$21.15	$21.15	$21.20
Purchase #5	$212.32	11.856%	$237.4927	$237.49	$237.50	$237.50
Purchase #6	$52.93	9.237%	$57.8191	$57.82	$57.80	$57.80
Purchase #7	$83.86	10.192%	$92.407	$92.41	$92.40	$92.40
7 purchase totals =	$675.46		$733.3919	$733.39	$733.40	$733.30