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	$88.45	10.463%	$97.7045	$97.70	$97.70	$97.70
Purchase #2	$34.87	7.288%	$37.4113	$37.41	$37.40	$37.40
Purchase #3	$67.25	7.187%	$72.0833	$72.08	$72.10	$72.10
Purchase #4	$140.80	10.177%	$155.1292	$155.13	$155.15	$155.10
Purchase #5	$76.53	12.157%	$85.8338	$85.83	$85.85	$85.80
Purchase #6	$132.90	7.635%	$143.0469	$143.05	$143.05	$143.00
Purchase #7	$168.43	13.578%	$191.2994	$191.30	$191.30	$191.30
7 purchase totals =	$709.23		$782.5084	$782.50	$782.55	$782.40