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	$114.66	10.338%	$126.5136	$126.51	$126.50	$126.50
Purchase #2	$168.96	5.551%	$178.339	$178.34	$178.35	$178.30
Purchase #3	$229.37	11.530%	$255.8164	$255.82	$255.80	$255.80
Purchase #4	$137.45	3.501%	$142.2621	$142.26	$142.25	$142.30
Purchase #5	$80.99	13.790%	$92.1585	$92.16	$92.15	$92.20
Purchase #6	$68.41	4.655%	$71.5945	$71.59	$71.60	$71.60
Purchase #7	$88.36	12.797%	$99.6674	$99.67	$99.65	$99.70
7 purchase totals =	$888.20		$966.3515	$966.35	$966.30	$966.40