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	$195.38	12.458%	$219.7204	$219.72	$219.70	$219.70
Purchase #2	$55.99	10.222%	$61.7133	$61.71	$61.70	$61.70
Purchase #3	$154.28	3.689%	$159.9714	$159.97	$159.95	$160.00
Purchase #4	$199.42	7.422%	$214.221	$214.22	$214.20	$214.20
Purchase #5	$210.56	5.854%	$222.8862	$222.89	$222.90	$222.90
Purchase #6	$109.83	4.238%	$114.4846	$114.48	$114.50	$114.50
Purchase #7	$22.84	12.630%	$25.7247	$25.72	$25.70	$25.70
7 purchase totals =	$948.30		$1,018.7216	$1,018.71	$1,018.65	$1,018.70