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	$206.31	7.755%	$222.3093	$222.31	$222.30	$222.30
Purchase #2	$192.39	13.525%	$218.4107	$218.41	$218.40	$218.40
Purchase #3	$90.66	5.678%	$95.8077	$95.81	$95.80	$95.80
Purchase #4	$114.72	4.163%	$119.4958	$119.50	$119.50	$119.50
Purchase #5	$212.86	3.171%	$219.6098	$219.61	$219.60	$219.60
Purchase #6	$211.73	11.622%	$236.3373	$236.34	$236.35	$236.30
Purchase #7	$97.64	5.867%	$103.3685	$103.37	$103.35	$103.40
7 purchase totals =	$1,126.31		$1,215.3391	$1,215.35	$1,215.30	$1,215.30