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	$238.92	5.447%	$251.934	$251.93	$251.95	$251.90
Purchase #2	$208.68	10.532%	$230.6582	$230.66	$230.65	$230.70
Purchase #3	$103.96	6.192%	$110.3972	$110.40	$110.40	$110.40
Purchase #4	$250.71	7.419%	$269.3102	$269.31	$269.30	$269.30
Purchase #5	$34.96	7.531%	$37.5928	$37.59	$37.60	$37.60
Purchase #6	$84.53	5.746%	$89.3871	$89.39	$89.40	$89.40
Purchase #7	$81.70	13.648%	$92.8504	$92.85	$92.85	$92.90
7 purchase totals =	$1,003.46		$1,082.1299	$1,082.13	$1,082.15	$1,082.20