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	$216.43	7.658%	$233.0042	$233.00	$233.00	$233.00
Purchase #2	$65.96	3.371%	$68.1835	$68.18	$68.20	$68.20
Purchase #3	$64.39	13.193%	$72.885	$72.89	$72.90	$72.90
Purchase #4	$146.67	12.299%	$164.7089	$164.71	$164.70	$164.70
Purchase #5	$143.50	6.226%	$152.4343	$152.43	$152.45	$152.40
Purchase #6	$30.29	3.870%	$31.4622	$31.46	$31.45	$31.50
Purchase #7	$57.56	9.175%	$62.8411	$62.84	$62.85	$62.80
7 purchase totals =	$724.80		$785.5192	$785.51	$785.55	$785.50