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	$108.29	3.170%	$111.7228	$111.72	$111.70	$111.70
Purchase #2	$205.86	9.581%	$225.5834	$225.58	$225.60	$225.60
Purchase #3	$154.64	11.539%	$172.4839	$172.48	$172.50	$172.50
Purchase #4	$234.69	5.168%	$246.8188	$246.82	$246.80	$246.80
Purchase #5	$136.99	6.512%	$145.9108	$145.91	$145.90	$145.90
Purchase #6	$138.53	11.616%	$154.6216	$154.62	$154.60	$154.60
Purchase #7	$112.35	6.432%	$119.5764	$119.58	$119.60	$119.60
7 purchase totals =	$1,091.35		$1,176.7177	$1,176.71	$1,176.70	$1,176.70