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	$193.77	11.670%	$216.383	$216.38	$216.40	$216.40
Purchase #2	$92.38	9.126%	$100.8106	$100.81	$100.80	$100.80
Purchase #3	$106.78	4.175%	$111.2381	$111.24	$111.25	$111.20
Purchase #4	$208.73	13.406%	$236.7123	$236.71	$236.70	$236.70
Purchase #5	$219.29	4.651%	$229.4892	$229.49	$229.50	$229.50
Purchase #6	$132.46	5.778%	$140.1135	$140.11	$140.10	$140.10
Purchase #7	$220.82	13.135%	$249.8247	$249.82	$249.80	$249.80
7 purchase totals =	$1,174.23		$1,284.5714	$1,284.56	$1,284.55	$1,284.50