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	$212.72	4.748%	$222.8199	$222.82	$222.80	$222.80
Purchase #2	$29.61	7.599%	$31.8601	$31.86	$31.85	$31.90
Purchase #3	$182.29	3.798%	$189.2134	$189.21	$189.20	$189.20
Purchase #4	$52.87	11.839%	$59.1293	$59.13	$59.15	$59.10
Purchase #5	$46.73	10.352%	$51.5675	$51.57	$51.55	$51.60
Purchase #6	$135.74	7.834%	$146.3739	$146.37	$146.35	$146.40
Purchase #7	$196.70	8.217%	$212.8628	$212.86	$212.85	$212.90
7 purchase totals =	$856.66		$913.8269	$913.82	$913.75	$913.90