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	$174.32	11.816%	$194.9177	$194.92	$194.90	$194.90
Purchase #2	$243.38	13.668%	$276.6452	$276.65	$276.65	$276.60
Purchase #3	$150.30	10.325%	$165.8185	$165.82	$165.80	$165.80
Purchase #4	$135.32	4.872%	$141.9128	$141.91	$141.90	$141.90
Purchase #5	$143.80	6.772%	$153.5381	$153.54	$153.55	$153.50
Purchase #6	$17.98	13.698%	$20.4429	$20.44	$20.45	$20.40
Purchase #7	$97.31	5.214%	$102.3837	$102.38	$102.40	$102.40
7 purchase totals =	$962.41		$1,055.6589	$1,055.66	$1,055.65	$1,055.50