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	$183.66	8.540%	$199.3446	$199.34	$199.35	$199.30
Purchase #2	$200.55	7.300%	$215.1902	$215.19	$215.20	$215.20
Purchase #3	$172.29	3.643%	$178.5665	$178.57	$178.55	$178.60
Purchase #4	$46.96	8.342%	$50.8774	$50.88	$50.90	$50.90
Purchase #5	$140.76	13.195%	$159.3333	$159.33	$159.35	$159.30
Purchase #6	$126.96	10.645%	$140.4749	$140.47	$140.45	$140.50
Purchase #7	$60.55	4.816%	$63.4661	$63.47	$63.45	$63.50
7 purchase totals =	$931.73		$1,007.2530	$1,007.25	$1,007.25	$1,007.30