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	$216.71	10.799%	$240.1125	$240.11	$240.10	$240.10
Purchase #2	$203.86	3.317%	$210.622	$210.62	$210.60	$210.60
Purchase #3	$176.72	6.437%	$188.0955	$188.10	$188.10	$188.10
Purchase #4	$150.29	11.513%	$167.5929	$167.59	$167.60	$167.60
Purchase #5	$149.29	11.679%	$166.7256	$166.73	$166.75	$166.70
Purchase #6	$208.93	6.687%	$222.9011	$222.90	$222.90	$222.90
Purchase #7	$115.79	11.219%	$128.7805	$128.78	$128.80	$128.80
7 purchase totals =	$1,221.59		$1,324.8301	$1,324.83	$1,324.85	$1,324.80