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	$242.83	4.310%	$253.296	$253.30	$253.30	$253.30
Purchase #2	$87.49	6.243%	$92.952	$92.95	$92.95	$93.00
Purchase #3	$101.58	4.259%	$105.9063	$105.91	$105.90	$105.90
Purchase #4	$123.79	11.422%	$137.9293	$137.93	$137.95	$137.90
Purchase #5	$140.43	8.158%	$151.8863	$151.89	$151.90	$151.90
Purchase #6	$114.60	8.777%	$124.6584	$124.66	$124.65	$124.70
Purchase #7	$204.28	8.132%	$220.892	$220.89	$220.90	$220.90
7 purchase totals =	$1,015.00		$1,087.5203	$1,087.53	$1,087.55	$1,087.60