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	$91.71	10.283%	$101.1405	$101.14	$101.15	$101.10
Purchase #2	$52.42	4.563%	$54.8119	$54.81	$54.80	$54.80
Purchase #3	$236.48	5.847%	$250.307	$250.31	$250.30	$250.30
Purchase #4	$185.79	7.836%	$200.3485	$200.35	$200.35	$200.30
Purchase #5	$29.52	8.156%	$31.9277	$31.93	$31.95	$31.90
Purchase #6	$53.43	7.322%	$57.3421	$57.34	$57.35	$57.30
Purchase #7	$216.74	6.530%	$230.8931	$230.89	$230.90	$230.90
7 purchase totals =	$866.09		$926.7708	$926.77	$926.80	$926.60