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	$20.73	4.310%	$21.6235	$21.62	$21.60	$21.60
Purchase #2	$195.83	3.344%	$202.3786	$202.38	$202.40	$202.40
Purchase #3	$191.41	10.176%	$210.8879	$210.89	$210.90	$210.90
Purchase #4	$52.47	7.549%	$56.431	$56.43	$56.45	$56.40
Purchase #5	$168.69	13.485%	$191.4378	$191.44	$191.45	$191.40
Purchase #6	$200.46	9.553%	$219.6099	$219.61	$219.60	$219.60
Purchase #7	$131.48	9.830%	$144.4045	$144.40	$144.40	$144.40
7 purchase totals =	$961.07		$1,046.7732	$1,046.77	$1,046.80	$1,046.70