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	$119.31	3.420%	$123.3904	$123.39	$123.40	$123.40
Purchase #2	$140.58	13.705%	$159.8465	$159.85	$159.85	$159.80
Purchase #3	$235.70	13.742%	$268.0899	$268.09	$268.10	$268.10
Purchase #4	$182.78	4.827%	$191.6028	$191.60	$191.60	$191.60
Purchase #5	$204.85	7.350%	$219.9065	$219.91	$219.90	$219.90
Purchase #6	$74.26	5.841%	$78.5975	$78.60	$78.60	$78.60
Purchase #7	$178.86	13.224%	$202.5124	$202.51	$202.50	$202.50
7 purchase totals =	$1,136.34		$1,243.9460	$1,243.95	$1,243.95	$1,243.90