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	$117.73	8.628%	$127.8877	$127.89	$127.90	$127.90
Purchase #2	$94.94	10.609%	$105.0122	$105.01	$105.00	$105.00
Purchase #3	$236.98	9.306%	$259.0334	$259.03	$259.05	$259.00
Purchase #4	$209.93	7.753%	$226.2059	$226.21	$226.20	$226.20
Purchase #5	$160.29	6.619%	$170.8996	$170.90	$170.90	$170.90
Purchase #6	$192.26	11.502%	$214.3737	$214.37	$214.35	$214.40
Purchase #7	$136.28	12.185%	$152.8857	$152.89	$152.90	$152.90
7 purchase totals =	$1,148.41		$1,256.2982	$1,256.30	$1,256.30	$1,256.30