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	$127.36	13.715%	$144.8274	$144.83	$144.85	$144.80
Purchase #2	$91.92	9.770%	$100.9006	$100.90	$100.90	$100.90
Purchase #3	$140.34	13.238%	$158.9182	$158.92	$158.90	$158.90
Purchase #4	$139.81	7.732%	$150.6201	$150.62	$150.60	$150.60
Purchase #5	$19.90	5.204%	$20.9356	$20.94	$20.95	$20.90
Purchase #6	$189.74	10.251%	$209.1902	$209.19	$209.20	$209.20
Purchase #7	$136.53	11.287%	$151.9401	$151.94	$151.95	$151.90
7 purchase totals =	$845.60		$937.3322	$937.34	$937.35	$937.20