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	$228.79	7.493%	$245.9332	$245.93	$245.95	$245.90
Purchase #2	$242.28	12.632%	$272.8848	$272.88	$272.90	$272.90
Purchase #3	$203.63	12.508%	$229.1	$229.10	$229.10	$229.10
Purchase #4	$217.58	9.409%	$238.0521	$238.05	$238.05	$238.10
Purchase #5	$188.46	4.260%	$196.4884	$196.49	$196.50	$196.50
Purchase #6	$137.40	10.317%	$151.5756	$151.58	$151.60	$151.60
Purchase #7	$131.91	3.168%	$136.0889	$136.09	$136.10	$136.10
7 purchase totals =	$1,350.05		$1,470.1230	$1,470.12	$1,470.20	$1,470.20