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	$169.26	13.427%	$191.9865	$191.99	$192.00	$192.00
Purchase #2	$135.64	11.699%	$151.5085	$151.51	$151.50	$151.50
Purchase #3	$132.82	7.624%	$142.9462	$142.95	$142.95	$142.90
Purchase #4	$76.47	7.278%	$82.0355	$82.04	$82.05	$82.00
Purchase #5	$63.27	13.213%	$71.6299	$71.63	$71.65	$71.60
Purchase #6	$83.74	10.192%	$92.2748	$92.27	$92.25	$92.30
Purchase #7	$107.26	4.823%	$112.4331	$112.43	$112.45	$112.40
7 purchase totals =	$768.46		$844.8145	$844.82	$844.85	$844.70