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	$178.94	4.209%	$186.4716	$186.47	$186.45	$186.50
Purchase #2	$34.31	9.224%	$37.4748	$37.47	$37.45	$37.50
Purchase #3	$229.94	10.682%	$254.5022	$254.50	$254.50	$254.50
Purchase #4	$217.51	4.570%	$227.4502	$227.45	$227.45	$227.50
Purchase #5	$22.76	9.423%	$24.9047	$24.90	$24.90	$24.90
Purchase #6	$104.64	11.672%	$116.8536	$116.85	$116.85	$116.90
Purchase #7	$49.66	13.585%	$56.4063	$56.41	$56.40	$56.40
7 purchase totals =	$837.76		$904.0634	$904.05	$904.00	$904.20