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	$90.37	4.151%	$94.1213	$94.12	$94.10	$94.10
Purchase #2	$101.70	3.802%	$105.5666	$105.57	$105.55	$105.60
Purchase #3	$154.63	4.698%	$161.8945	$161.89	$161.90	$161.90
Purchase #4	$57.73	11.499%	$64.3684	$64.37	$64.35	$64.40
Purchase #5	$242.67	4.854%	$254.4492	$254.45	$254.45	$254.40
Purchase #6	$146.39	12.575%	$164.7985	$164.80	$164.80	$164.80
Purchase #7	$94.69	10.660%	$104.784	$104.78	$104.80	$104.80
7 purchase totals =	$888.18		$949.9825	$949.98	$949.95	$950.00