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	$136.34	11.814%	$152.4472	$152.45	$152.45	$152.40
Purchase #2	$42.89	12.528%	$48.2633	$48.26	$48.25	$48.30
Purchase #3	$141.50	6.117%	$150.1556	$150.16	$150.15	$150.20
Purchase #4	$242.88	8.423%	$263.3378	$263.34	$263.35	$263.30
Purchase #5	$221.83	4.547%	$231.9166	$231.92	$231.90	$231.90
Purchase #6	$198.47	5.265%	$208.9194	$208.92	$208.90	$208.90
Purchase #7	$27.82	9.442%	$30.4468	$30.45	$30.45	$30.40
7 purchase totals =	$1,011.73		$1,085.4867	$1,085.50	$1,085.45	$1,085.40