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	$100.34	4.471%	$104.8262	$104.83	$104.85	$104.80
Purchase #2	$249.77	11.280%	$277.9441	$277.94	$277.95	$277.90
Purchase #3	$182.89	8.658%	$198.7246	$198.72	$198.70	$198.70
Purchase #4	$140.25	7.309%	$150.5009	$150.50	$150.50	$150.50
Purchase #5	$14.95	4.257%	$15.5864	$15.59	$15.60	$15.60
Purchase #6	$162.31	13.746%	$184.6211	$184.62	$184.60	$184.60
Purchase #7	$65.38	8.189%	$70.734	$70.73	$70.75	$70.70
7 purchase totals =	$915.89		$1,002.9373	$1,002.93	$1,002.95	$1,002.80