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	$35.98	9.761%	$39.492	$39.49	$39.50	$39.50
Purchase #2	$60.89	11.543%	$67.9185	$67.92	$67.90	$67.90
Purchase #3	$180.25	8.381%	$195.3568	$195.36	$195.35	$195.40
Purchase #4	$223.81	8.410%	$242.6324	$242.63	$242.65	$242.60
Purchase #5	$154.62	11.367%	$172.1957	$172.20	$172.20	$172.20
Purchase #6	$84.30	9.691%	$92.4695	$92.47	$92.45	$92.50
Purchase #7	$121.47	8.261%	$131.5046	$131.50	$131.50	$131.50
7 purchase totals =	$861.32		$941.5695	$941.57	$941.55	$941.60