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	$244.53	9.461%	$267.665	$267.67	$267.65	$267.70
Purchase #2	$227.28	13.726%	$258.4765	$258.48	$258.50	$258.50
Purchase #3	$90.83	13.401%	$103.0021	$103.00	$103.00	$103.00
Purchase #4	$50.53	9.199%	$55.1783	$55.18	$55.20	$55.20
Purchase #5	$231.29	8.268%	$250.4131	$250.41	$250.40	$250.40
Purchase #6	$78.51	5.444%	$82.7841	$82.78	$82.80	$82.80
Purchase #7	$70.28	8.668%	$76.3719	$76.37	$76.35	$76.40
7 purchase totals =	$993.25		$1,093.8910	$1,093.89	$1,093.90	$1,094.00