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	$219.60	12.723%	$247.5397	$247.54	$247.55	$247.50
Purchase #2	$47.84	6.273%	$50.841	$50.84	$50.85	$50.80
Purchase #3	$150.85	12.356%	$169.489	$169.49	$169.50	$169.50
Purchase #4	$45.97	13.847%	$52.3355	$52.34	$52.35	$52.30
Purchase #5	$77.39	6.256%	$82.2315	$82.23	$82.25	$82.20
Purchase #6	$208.75	10.447%	$230.5581	$230.56	$230.55	$230.60
Purchase #7	$229.61	8.686%	$249.5539	$249.55	$249.55	$249.60
7 purchase totals =	$980.01		$1,082.5487	$1,082.55	$1,082.60	$1,082.50