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	$244.61	13.286%	$277.1089	$277.11	$277.10	$277.10
Purchase #2	$184.83	10.437%	$204.1207	$204.12	$204.10	$204.10
Purchase #3	$27.73	12.619%	$31.2292	$31.23	$31.25	$31.20
Purchase #4	$161.60	4.277%	$168.5116	$168.51	$168.50	$168.50
Purchase #5	$180.68	8.553%	$196.1336	$196.13	$196.15	$196.10
Purchase #6	$105.62	3.824%	$109.6589	$109.66	$109.65	$109.70
Purchase #7	$147.92	10.554%	$163.5315	$163.53	$163.55	$163.50
7 purchase totals =	$1,052.99		$1,150.2944	$1,150.29	$1,150.30	$1,150.20