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	$61.31	6.202%	$65.1124	$65.11	$65.10	$65.10
Purchase #2	$41.67	10.408%	$46.007	$46.01	$46.00	$46.00
Purchase #3	$161.92	4.264%	$168.8243	$168.82	$168.80	$168.80
Purchase #4	$26.51	3.847%	$27.5298	$27.53	$27.55	$27.50
Purchase #5	$39.61	4.777%	$41.5022	$41.50	$41.50	$41.50
Purchase #6	$30.75	11.435%	$34.2663	$34.27	$34.25	$34.30
Purchase #7	$152.92	8.596%	$166.065	$166.07	$166.05	$166.10
7 purchase totals =	$514.69		$549.3070	$549.31	$549.25	$549.30