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	$161.71	12.507%	$181.9351	$181.94	$181.95	$181.90
Purchase #2	$130.93	12.618%	$147.4507	$147.45	$147.45	$147.50
Purchase #3	$9.51	11.574%	$10.6107	$10.61	$10.60	$10.60
Purchase #4	$37.25	13.398%	$42.2408	$42.24	$42.25	$42.20
Purchase #5	$43.49	13.707%	$49.4512	$49.45	$49.45	$49.50
Purchase #6	$67.69	7.610%	$72.8412	$72.84	$72.85	$72.80
Purchase #7	$218.52	6.437%	$232.5861	$232.59	$232.60	$232.60
7 purchase totals =	$669.10		$737.1158	$737.12	$737.15	$737.10