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	$226.83	3.166%	$234.0114	$234.01	$234.00	$234.00
Purchase #2	$179.38	6.294%	$190.6702	$190.67	$190.65	$190.70
Purchase #3	$222.97	9.333%	$243.7798	$243.78	$243.80	$243.80
Purchase #4	$45.56	4.388%	$47.5592	$47.56	$47.55	$47.60
Purchase #5	$40.43	6.144%	$42.914	$42.91	$42.90	$42.90
Purchase #6	$56.84	13.696%	$64.6248	$64.62	$64.60	$64.60
Purchase #7	$230.36	11.308%	$256.4091	$256.41	$256.40	$256.40
7 purchase totals =	$1,002.37		$1,079.9685	$1,079.96	$1,079.90	$1,080.00