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	$94.29	8.697%	$102.4904	$102.49	$102.50	$102.50
Purchase #2	$60.71	4.193%	$63.2556	$63.26	$63.25	$63.30
Purchase #3	$103.51	8.573%	$112.3839	$112.38	$112.40	$112.40
Purchase #4	$59.74	9.331%	$65.3143	$65.31	$65.30	$65.30
Purchase #5	$134.40	3.507%	$139.1134	$139.11	$139.10	$139.10
Purchase #6	$167.78	10.607%	$185.5764	$185.58	$185.60	$185.60
Purchase #7	$29.84	9.857%	$32.7813	$32.78	$32.80	$32.80
7 purchase totals =	$650.27		$700.9153	$700.91	$700.95	$701.00