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	$111.53	11.493%	$124.3481	$124.35	$124.35	$124.30
Purchase #2	$29.87	13.323%	$33.8496	$33.85	$33.85	$33.80
Purchase #3	$144.36	13.838%	$164.3365	$164.34	$164.35	$164.30
Purchase #4	$31.92	3.651%	$33.0854	$33.09	$33.10	$33.10
Purchase #5	$240.89	12.643%	$271.3457	$271.35	$271.35	$271.30
Purchase #6	$32.62	13.791%	$37.1186	$37.12	$37.10	$37.10
Purchase #7	$44.54	7.582%	$47.917	$47.92	$47.90	$47.90
7 purchase totals =	$635.73		$712.0009	$712.02	$712.00	$711.80