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	$190.83	11.717%	$213.1896	$213.19	$213.20	$213.20
Purchase #2	$128.57	13.529%	$145.9642	$145.96	$145.95	$146.00
Purchase #3	$52.63	8.808%	$57.2657	$57.27	$57.25	$57.30
Purchase #4	$208.98	6.613%	$222.7998	$222.80	$222.80	$222.80
Purchase #5	$37.81	11.206%	$42.047	$42.05	$42.05	$42.00
Purchase #6	$187.42	12.811%	$211.4304	$211.43	$211.45	$211.40
Purchase #7	$144.94	10.806%	$160.6022	$160.60	$160.60	$160.60
7 purchase totals =	$951.18		$1,053.2989	$1,053.30	$1,053.30	$1,053.30