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	$247.63	4.368%	$258.4465	$258.45	$258.45	$258.40
Purchase #2	$184.73	6.223%	$196.2257	$196.23	$196.25	$196.20
Purchase #3	$208.66	8.228%	$225.8285	$225.83	$225.85	$225.80
Purchase #4	$244.35	7.198%	$261.9383	$261.94	$261.95	$261.90
Purchase #5	$88.41	5.435%	$93.2151	$93.22	$93.20	$93.20
Purchase #6	$238.30	5.155%	$250.5844	$250.58	$250.60	$250.60
Purchase #7	$19.32	12.382%	$21.7122	$21.71	$21.70	$21.70
7 purchase totals =	$1,231.40		$1,307.9507	$1,307.96	$1,308.00	$1,307.80