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	$200.94	11.457%	$223.9617	$223.96	$223.95	$224.00
Purchase #2	$247.75	10.767%	$274.4252	$274.43	$274.45	$274.40
Purchase #3	$151.57	8.557%	$164.5398	$164.54	$164.55	$164.50
Purchase #4	$47.35	10.861%	$52.4927	$52.49	$52.50	$52.50
Purchase #5	$137.78	5.267%	$145.0369	$145.04	$145.05	$145.00
Purchase #6	$55.46	4.226%	$57.8037	$57.80	$57.80	$57.80
Purchase #7	$116.46	10.692%	$128.9119	$128.91	$128.90	$128.90
7 purchase totals =	$957.31		$1,047.1719	$1,047.17	$1,047.20	$1,047.10