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	$153.94	12.217%	$172.7468	$172.75	$172.75	$172.70
Purchase #2	$225.31	12.496%	$253.4647	$253.46	$253.45	$253.50
Purchase #3	$192.37	8.289%	$208.3155	$208.32	$208.30	$208.30
Purchase #4	$129.83	8.566%	$140.9512	$140.95	$140.95	$141.00
Purchase #5	$52.96	5.373%	$55.8055	$55.81	$55.80	$55.80
Purchase #6	$106.33	6.743%	$113.4998	$113.50	$113.50	$113.50
Purchase #7	$196.40	6.436%	$209.0403	$209.04	$209.05	$209.00
7 purchase totals =	$1,057.14		$1,153.8238	$1,153.83	$1,153.80	$1,153.80