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	$210.34	10.825%	$233.1093	$233.11	$233.10	$233.10
Purchase #2	$37.81	4.489%	$39.5073	$39.51	$39.50	$39.50
Purchase #3	$237.74	7.336%	$255.1806	$255.18	$255.20	$255.20
Purchase #4	$177.25	3.684%	$183.7799	$183.78	$183.80	$183.80
Purchase #5	$72.32	7.369%	$77.6493	$77.65	$77.65	$77.60
Purchase #6	$177.54	11.782%	$198.4578	$198.46	$198.45	$198.50
Purchase #7	$30.28	5.137%	$31.8355	$31.84	$31.85	$31.80
7 purchase totals =	$943.28		$1,019.5197	$1,019.53	$1,019.55	$1,019.50