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	$145.83	13.622%	$165.695	$165.70	$165.70	$165.70
Purchase #2	$200.96	6.807%	$214.6393	$214.64	$214.65	$214.60
Purchase #3	$72.37	6.813%	$77.3006	$77.30	$77.30	$77.30
Purchase #4	$203.72	5.797%	$215.5296	$215.53	$215.55	$215.50
Purchase #5	$29.27	13.468%	$33.2121	$33.21	$33.20	$33.20
Purchase #6	$58.94	13.291%	$66.7737	$66.77	$66.75	$66.80
Purchase #7	$222.51	10.695%	$246.3074	$246.31	$246.30	$246.30
7 purchase totals =	$933.60		$1,019.4577	$1,019.46	$1,019.45	$1,019.40