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	$40.75	7.447%	$43.7847	$43.78	$43.80	$43.80
Purchase #2	$187.46	11.446%	$208.9167	$208.92	$208.90	$208.90
Purchase #3	$16.82	8.390%	$18.2312	$18.23	$18.25	$18.20
Purchase #4	$94.89	12.525%	$106.775	$106.78	$106.80	$106.80
Purchase #5	$196.34	12.826%	$221.5226	$221.52	$221.50	$221.50
Purchase #6	$115.71	4.152%	$120.5143	$120.51	$120.50	$120.50
Purchase #7	$204.33	4.104%	$212.7157	$212.72	$212.70	$212.70
7 purchase totals =	$856.30		$932.4602	$932.46	$932.45	$932.40