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	$175.89	8.383%	$190.6349	$190.63	$190.65	$190.60
Purchase #2	$245.86	11.594%	$274.365	$274.37	$274.35	$274.40
Purchase #3	$235.53	8.395%	$255.3027	$255.30	$255.30	$255.30
Purchase #4	$62.39	4.452%	$65.1676	$65.17	$65.15	$65.20
Purchase #5	$52.35	6.392%	$55.6962	$55.70	$55.70	$55.70
Purchase #6	$208.95	3.345%	$215.9394	$215.94	$215.95	$215.90
Purchase #7	$164.78	13.693%	$187.3433	$187.34	$187.35	$187.30
7 purchase totals =	$1,145.75		$1,244.4491	$1,244.45	$1,244.45	$1,244.40