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	$198.61	8.775%	$216.038	$216.04	$216.05	$216.00
Purchase #2	$40.57	4.360%	$42.3389	$42.34	$42.35	$42.30
Purchase #3	$94.33	9.721%	$103.4998	$103.50	$103.50	$103.50
Purchase #4	$199.73	13.719%	$227.131	$227.13	$227.15	$227.10
Purchase #5	$101.49	3.531%	$105.0736	$105.07	$105.05	$105.10
Purchase #6	$115.59	10.709%	$127.9685	$127.97	$127.95	$128.00
Purchase #7	$136.54	7.544%	$146.8406	$146.84	$146.85	$146.80
7 purchase totals =	$886.86		$968.8904	$968.89	$968.90	$968.80