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	$57.74	5.408%	$60.8626	$60.86	$60.85	$60.90
Purchase #2	$193.32	10.504%	$213.6263	$213.63	$213.65	$213.60
Purchase #3	$247.79	7.715%	$266.907	$266.91	$266.90	$266.90
Purchase #4	$88.96	13.378%	$100.8611	$100.86	$100.85	$100.90
Purchase #5	$148.61	6.581%	$158.39	$158.39	$158.40	$158.40
Purchase #6	$118.41	10.708%	$131.0893	$131.09	$131.10	$131.10
Purchase #7	$62.52	6.194%	$66.3925	$66.39	$66.40	$66.40
7 purchase totals =	$917.35		$998.1288	$998.13	$998.15	$998.20