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	$185.86	5.566%	$196.205	$196.21	$196.20	$196.20
Purchase #2	$127.65	9.115%	$139.2853	$139.29	$139.30	$139.30
Purchase #3	$227.64	10.425%	$251.3715	$251.37	$251.35	$251.40
Purchase #4	$210.91	4.681%	$220.7827	$220.78	$220.80	$220.80
Purchase #5	$179.70	9.404%	$196.599	$196.60	$196.60	$196.60
Purchase #6	$143.56	11.409%	$159.9388	$159.94	$159.95	$159.90
Purchase #7	$47.97	3.211%	$49.5103	$49.51	$49.50	$49.50
7 purchase totals =	$1,123.29		$1,213.6926	$1,213.70	$1,213.70	$1,213.70