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	$35.38	8.355%	$38.336	$38.34	$38.35	$38.30
Purchase #2	$25.47	10.256%	$28.0822	$28.08	$28.10	$28.10
Purchase #3	$134.89	5.164%	$141.8557	$141.86	$141.85	$141.90
Purchase #4	$243.35	5.301%	$256.25	$256.25	$256.25	$256.30
Purchase #5	$236.51	12.412%	$265.8656	$265.87	$265.85	$265.90
Purchase #6	$29.48	5.521%	$31.1076	$31.11	$31.10	$31.10
Purchase #7	$236.31	5.859%	$250.1554	$250.16	$250.15	$250.20
7 purchase totals =	$941.39		$1,011.6525	$1,011.67	$1,011.65	$1,011.80