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	$67.68	5.246%	$71.2305	$71.23	$71.25	$71.20
Purchase #2	$120.83	7.779%	$130.2294	$130.23	$130.25	$130.20
Purchase #3	$231.93	13.630%	$263.5421	$263.54	$263.55	$263.50
Purchase #4	$36.89	4.550%	$38.5685	$38.57	$38.55	$38.60
Purchase #5	$217.73	12.300%	$244.5108	$244.51	$244.50	$244.50
Purchase #6	$155.87	10.554%	$172.3205	$172.32	$172.30	$172.30
Purchase #7	$130.78	5.291%	$137.6996	$137.70	$137.70	$137.70
7 purchase totals =	$961.71		$1,058.1014	$1,058.10	$1,058.10	$1,058.00