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	$159.64	12.161%	$179.0538	$179.05	$179.05	$179.10
Purchase #2	$185.33	8.178%	$200.4863	$200.49	$200.50	$200.50
Purchase #3	$57.72	13.214%	$65.3471	$65.35	$65.35	$65.30
Purchase #4	$176.36	8.216%	$190.8497	$190.85	$190.85	$190.80
Purchase #5	$246.96	3.755%	$256.2333	$256.23	$256.25	$256.20
Purchase #6	$40.70	10.203%	$44.8526	$44.85	$44.85	$44.90
Purchase #7	$131.30	10.838%	$145.5303	$145.53	$145.55	$145.50
7 purchase totals =	$998.01		$1,082.3531	$1,082.35	$1,082.40	$1,082.30