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	$22.43	11.568%	$25.0247	$25.02	$25.00	$25.00
Purchase #2	$78.68	6.181%	$83.5432	$83.54	$83.55	$83.50
Purchase #3	$52.87	12.137%	$59.2868	$59.29	$59.30	$59.30
Purchase #4	$172.82	4.154%	$179.9989	$180.00	$180.00	$180.00
Purchase #5	$151.77	11.593%	$169.3647	$169.36	$169.35	$169.40
Purchase #6	$60.65	13.732%	$68.9785	$68.98	$69.00	$69.00
Purchase #7	$41.57	10.113%	$45.774	$45.77	$45.75	$45.80
7 purchase totals =	$580.79		$631.9708	$631.96	$631.95	$632.00