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	$90.90	7.550%	$97.763	$97.76	$97.75	$97.80
Purchase #2	$240.34	10.869%	$266.4626	$266.46	$266.45	$266.50
Purchase #3	$102.55	8.667%	$111.438	$111.44	$111.45	$111.40
Purchase #4	$197.84	6.441%	$210.5829	$210.58	$210.60	$210.60
Purchase #5	$58.94	12.437%	$66.2704	$66.27	$66.25	$66.30
Purchase #6	$90.76	4.175%	$94.5492	$94.55	$94.55	$94.50
Purchase #7	$103.65	4.648%	$108.4677	$108.47	$108.45	$108.50
7 purchase totals =	$884.98		$955.5338	$955.53	$955.50	$955.60