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	$35.95	3.115%	$37.0698	$37.07	$37.05	$37.10
Purchase #2	$50.34	4.855%	$52.784	$52.78	$52.80	$52.80
Purchase #3	$143.36	9.144%	$156.4688	$156.47	$156.45	$156.50
Purchase #4	$147.57	6.199%	$156.7179	$156.72	$156.70	$156.70
Purchase #5	$84.31	13.719%	$95.8765	$95.88	$95.90	$95.90
Purchase #6	$107.60	4.563%	$112.5098	$112.51	$112.50	$112.50
Purchase #7	$200.31	7.859%	$216.0524	$216.05	$216.05	$216.10
7 purchase totals =	$769.44		$827.4792	$827.48	$827.45	$827.60