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	$182.68	6.325%	$194.2345	$194.23	$194.25	$194.20
Purchase #2	$83.85	8.221%	$90.7433	$90.74	$90.75	$90.70
Purchase #3	$99.27	7.712%	$106.9257	$106.93	$106.95	$106.90
Purchase #4	$85.71	3.121%	$88.385	$88.39	$88.40	$88.40
Purchase #5	$100.77	3.802%	$104.6013	$104.60	$104.60	$104.60
Purchase #6	$138.85	11.136%	$154.3123	$154.31	$154.30	$154.30
Purchase #7	$21.48	6.399%	$22.8545	$22.85	$22.85	$22.90
7 purchase totals =	$712.61		$762.0566	$762.05	$762.10	$762.00