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	$112.27	3.769%	$116.5015	$116.50	$116.50	$116.50
Purchase #2	$159.39	13.284%	$180.5634	$180.56	$180.55	$180.60
Purchase #3	$98.59	3.243%	$101.7873	$101.79	$101.80	$101.80
Purchase #4	$232.59	10.231%	$256.3863	$256.39	$256.40	$256.40
Purchase #5	$119.87	13.137%	$135.6173	$135.62	$135.60	$135.60
Purchase #6	$34.88	6.755%	$37.2361	$37.24	$37.25	$37.20
Purchase #7	$208.71	3.213%	$215.4159	$215.42	$215.40	$215.40
7 purchase totals =	$966.30		$1,043.5078	$1,043.52	$1,043.50	$1,043.50