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	$117.44	9.516%	$128.6156	$128.62	$128.60	$128.60
Purchase #2	$200.37	13.531%	$227.4821	$227.48	$227.50	$227.50
Purchase #3	$187.81	4.805%	$196.8343	$196.83	$196.85	$196.80
Purchase #4	$23.74	13.474%	$26.9387	$26.94	$26.95	$26.90
Purchase #5	$216.37	11.265%	$240.7441	$240.74	$240.75	$240.70
Purchase #6	$88.55	13.468%	$100.4759	$100.48	$100.50	$100.50
Purchase #7	$249.40	4.727%	$261.1891	$261.19	$261.20	$261.20
7 purchase totals =	$1,083.68		$1,182.2798	$1,182.28	$1,182.35	$1,182.20