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	$12.34	13.500%	$14.0059	$14.01	$14.00	$14.00
Purchase #2	$165.59	4.326%	$172.7534	$172.75	$172.75	$172.80
Purchase #3	$216.56	8.822%	$235.6649	$235.66	$235.65	$235.70
Purchase #4	$139.81	11.595%	$156.021	$156.02	$156.00	$156.00
Purchase #5	$139.59	13.465%	$158.3858	$158.39	$158.40	$158.40
Purchase #6	$165.50	9.637%	$181.4492	$181.45	$181.45	$181.40
Purchase #7	$146.37	11.514%	$163.223	$163.22	$163.20	$163.20
7 purchase totals =	$985.76		$1,081.5032	$1,081.50	$1,081.45	$1,081.50