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	$187.85	13.568%	$213.3375	$213.34	$213.35	$213.30
Purchase #2	$56.54	8.704%	$61.4612	$61.46	$61.45	$61.50
Purchase #3	$247.71	9.582%	$271.4456	$271.45	$271.45	$271.40
Purchase #4	$65.59	8.725%	$71.3127	$71.31	$71.30	$71.30
Purchase #5	$202.41	12.560%	$227.8327	$227.83	$227.85	$227.80
Purchase #6	$95.35	10.363%	$105.2311	$105.23	$105.25	$105.20
Purchase #7	$180.78	8.221%	$195.6419	$195.64	$195.65	$195.60
7 purchase totals =	$1,036.23		$1,146.2627	$1,146.26	$1,146.30	$1,146.10