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	$220.86	7.480%	$237.3803	$237.38	$237.40	$237.40
Purchase #2	$218.78	3.420%	$226.2623	$226.26	$226.25	$226.30
Purchase #3	$84.79	4.174%	$88.3291	$88.33	$88.35	$88.30
Purchase #4	$30.93	8.381%	$33.5222	$33.52	$33.50	$33.50
Purchase #5	$37.56	8.375%	$40.7057	$40.71	$40.70	$40.70
Purchase #6	$114.28	11.267%	$127.1559	$127.16	$127.15	$127.20
Purchase #7	$250.74	3.105%	$258.5255	$258.53	$258.55	$258.50
7 purchase totals =	$957.94		$1,011.8810	$1,011.89	$1,011.90	$1,011.90