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	$226.88	6.852%	$242.4258	$242.43	$242.45	$242.40
Purchase #2	$55.29	3.783%	$57.3816	$57.38	$57.40	$57.40
Purchase #3	$147.61	13.644%	$167.7499	$167.75	$167.75	$167.70
Purchase #4	$140.67	11.782%	$157.2437	$157.24	$157.25	$157.20
Purchase #5	$161.48	10.418%	$178.303	$178.30	$178.30	$178.30
Purchase #6	$64.58	10.154%	$71.1375	$71.14	$71.15	$71.10
Purchase #7	$154.88	11.602%	$172.8492	$172.85	$172.85	$172.80
7 purchase totals =	$951.39		$1,047.0907	$1,047.09	$1,047.15	$1,046.90