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	$226.42	12.189%	$254.0183	$254.02	$254.00	$254.00
Purchase #2	$40.92	3.748%	$42.4537	$42.45	$42.45	$42.50
Purchase #3	$59.84	12.261%	$67.177	$67.18	$67.20	$67.20
Purchase #4	$76.26	9.793%	$83.7281	$83.73	$83.75	$83.70
Purchase #5	$135.37	7.193%	$145.1072	$145.11	$145.10	$145.10
Purchase #6	$184.67	6.537%	$196.7419	$196.74	$196.75	$196.70
Purchase #7	$210.84	3.627%	$218.4872	$218.49	$218.50	$218.50
7 purchase totals =	$934.32		$1,007.7134	$1,007.72	$1,007.75	$1,007.70