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	$174.89	3.778%	$181.4973	$181.50	$181.50	$181.50
Purchase #2	$223.61	9.635%	$245.1548	$245.15	$245.15	$245.20
Purchase #3	$6.29	8.676%	$6.8357	$6.84	$6.85	$6.80
Purchase #4	$220.52	9.240%	$240.896	$240.90	$240.90	$240.90
Purchase #5	$148.47	9.136%	$162.0342	$162.03	$162.05	$162.00
Purchase #6	$131.66	5.861%	$139.3766	$139.38	$139.40	$139.40
Purchase #7	$225.31	9.854%	$247.512	$247.51	$247.50	$247.50
7 purchase totals =	$1,130.75		$1,223.3066	$1,223.31	$1,223.35	$1,223.30