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	$231.59	6.109%	$245.7378	$245.74	$245.75	$245.70
Purchase #2	$108.69	3.858%	$112.8833	$112.88	$112.90	$112.90
Purchase #3	$131.59	12.377%	$147.8769	$147.88	$147.90	$147.90
Purchase #4	$192.58	13.742%	$219.0443	$219.04	$219.05	$219.00
Purchase #5	$229.45	6.601%	$244.596	$244.60	$244.60	$244.60
Purchase #6	$12.90	5.321%	$13.5864	$13.59	$13.60	$13.60
Purchase #7	$139.79	7.775%	$150.6587	$150.66	$150.65	$150.70
7 purchase totals =	$1,046.59		$1,134.3834	$1,134.39	$1,134.45	$1,134.40