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	$216.71	5.734%	$229.1362	$229.14	$229.15	$229.10
Purchase #2	$126.36	11.549%	$140.9533	$140.95	$140.95	$141.00
Purchase #3	$82.55	6.709%	$88.0883	$88.09	$88.10	$88.10
Purchase #4	$162.69	6.743%	$173.6602	$173.66	$173.65	$173.70
Purchase #5	$11.54	11.116%	$12.8228	$12.82	$12.80	$12.80
Purchase #6	$171.60	8.184%	$185.6437	$185.64	$185.65	$185.60
Purchase #7	$232.39	4.820%	$243.5912	$243.59	$243.60	$243.60
7 purchase totals =	$1,003.84		$1,073.8957	$1,073.89	$1,073.90	$1,073.90