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	$154.56	6.115%	$164.0113	$164.01	$164.00	$164.00
Purchase #2	$223.52	5.836%	$236.5646	$236.56	$236.55	$236.60
Purchase #3	$221.96	5.820%	$234.8781	$234.88	$234.90	$234.90
Purchase #4	$40.49	3.741%	$42.0047	$42.00	$42.00	$42.00
Purchase #5	$230.71	8.401%	$250.0919	$250.09	$250.10	$250.10
Purchase #6	$243.88	7.504%	$262.1808	$262.18	$262.20	$262.20
Purchase #7	$37.71	11.625%	$42.0938	$42.09	$42.10	$42.10
7 purchase totals =	$1,152.83		$1,231.8252	$1,231.81	$1,231.85	$1,231.90