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	$111.78	11.795%	$124.9645	$124.96	$124.95	$125.00
Purchase #2	$82.79	4.389%	$86.4237	$86.42	$86.40	$86.40
Purchase #3	$87.56	8.755%	$95.2259	$95.23	$95.25	$95.20
Purchase #4	$104.27	11.285%	$116.0369	$116.04	$116.05	$116.00
Purchase #5	$137.46	6.420%	$146.2849	$146.28	$146.30	$146.30
Purchase #6	$159.32	12.473%	$179.192	$179.19	$179.20	$179.20
Purchase #7	$235.71	3.472%	$243.8939	$243.89	$243.90	$243.90
7 purchase totals =	$918.89		$992.0218	$992.01	$992.05	$992.00