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	$231.77	10.150%	$255.2947	$255.29	$255.30	$255.30
Purchase #2	$125.97	4.138%	$131.1826	$131.18	$131.20	$131.20
Purchase #3	$80.34	7.629%	$86.4691	$86.47	$86.45	$86.50
Purchase #4	$136.46	10.721%	$151.0899	$151.09	$151.10	$151.10
Purchase #5	$180.40	11.137%	$200.4911	$200.49	$200.50	$200.50
Purchase #6	$111.30	5.727%	$117.6742	$117.67	$117.65	$117.70
Purchase #7	$242.57	5.634%	$256.2364	$256.24	$256.25	$256.20
7 purchase totals =	$1,108.81		$1,198.4380	$1,198.43	$1,198.45	$1,198.50