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	$147.34	4.454%	$153.9025	$153.90	$153.90	$153.90
Purchase #2	$111.87	10.849%	$124.0068	$124.01	$124.00	$124.00
Purchase #3	$228.90	8.614%	$248.6174	$248.62	$248.60	$248.60
Purchase #4	$162.37	10.187%	$178.9106	$178.91	$178.90	$178.90
Purchase #5	$141.44	6.683%	$150.8924	$150.89	$150.90	$150.90
Purchase #6	$29.80	11.496%	$33.2258	$33.23	$33.25	$33.20
Purchase #7	$225.77	3.499%	$233.6697	$233.67	$233.65	$233.70
7 purchase totals =	$1,047.49		$1,123.2252	$1,123.23	$1,123.20	$1,123.20