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	$211.31	7.433%	$227.0167	$227.02	$227.00	$227.00
Purchase #2	$103.77	8.709%	$112.8073	$112.81	$112.80	$112.80
Purchase #3	$113.38	8.570%	$123.0967	$123.10	$123.10	$123.10
Purchase #4	$171.86	5.168%	$180.7417	$180.74	$180.75	$180.70
Purchase #5	$114.50	12.434%	$128.7369	$128.74	$128.75	$128.70
Purchase #6	$103.27	9.381%	$112.9578	$112.96	$112.95	$113.00
Purchase #7	$243.36	6.487%	$259.1468	$259.15	$259.15	$259.10
7 purchase totals =	$1,061.45		$1,144.5039	$1,144.52	$1,144.50	$1,144.40