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	$216.44	6.341%	$230.1645	$230.16	$230.15	$230.20
Purchase #2	$198.95	11.642%	$222.1118	$222.11	$222.10	$222.10
Purchase #3	$190.44	3.214%	$196.5607	$196.56	$196.55	$196.60
Purchase #4	$184.87	6.122%	$196.1877	$196.19	$196.20	$196.20
Purchase #5	$52.50	13.573%	$59.6258	$59.63	$59.65	$59.60
Purchase #6	$189.97	6.578%	$202.4662	$202.47	$202.45	$202.50
Purchase #7	$91.55	12.692%	$103.1695	$103.17	$103.15	$103.20
7 purchase totals =	$1,124.72		$1,210.2862	$1,210.29	$1,210.25	$1,210.40