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	$42.95	7.541%	$46.1889	$46.19	$46.20	$46.20
Purchase #2	$245.68	13.831%	$279.66	$279.66	$279.65	$279.70
Purchase #3	$209.93	13.754%	$238.8038	$238.80	$238.80	$238.80
Purchase #4	$161.98	8.597%	$175.9054	$175.91	$175.90	$175.90
Purchase #5	$177.51	10.686%	$196.4787	$196.48	$196.50	$196.50
Purchase #6	$22.52	12.523%	$25.3402	$25.34	$25.35	$25.30
Purchase #7	$47.89	5.262%	$50.41	$50.41	$50.40	$50.40
7 purchase totals =	$908.46		$1,012.7870	$1,012.79	$1,012.80	$1,012.80