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	$89.62	9.473%	$98.1097	$98.11	$98.10	$98.10
Purchase #2	$210.85	11.658%	$235.4309	$235.43	$235.45	$235.40
Purchase #3	$169.92	12.110%	$190.4973	$190.50	$190.50	$190.50
Purchase #4	$92.59	7.693%	$99.7129	$99.71	$99.70	$99.70
Purchase #5	$59.75	13.421%	$67.769	$67.77	$67.75	$67.80
Purchase #6	$51.65	11.474%	$57.5763	$57.58	$57.60	$57.60
Purchase #7	$233.86	4.110%	$243.4716	$243.47	$243.45	$243.50
7 purchase totals =	$908.24		$992.5677	$992.57	$992.55	$992.60