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	$53.88	13.816%	$61.3241	$61.32	$61.30	$61.30
Purchase #2	$91.46	10.313%	$100.8923	$100.89	$100.90	$100.90
Purchase #3	$105.34	12.864%	$118.8909	$118.89	$118.90	$118.90
Purchase #4	$165.36	4.698%	$173.1286	$173.13	$173.15	$173.10
Purchase #5	$138.48	7.376%	$148.6943	$148.69	$148.70	$148.70
Purchase #6	$136.40	3.131%	$140.6707	$140.67	$140.65	$140.70
Purchase #7	$158.44	13.708%	$180.159	$180.16	$180.15	$180.20
7 purchase totals =	$849.36		$923.7599	$923.75	$923.75	$923.80