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	$164.26	10.556%	$181.5993	$181.60	$181.60	$181.60
Purchase #2	$101.69	3.167%	$104.9105	$104.91	$104.90	$104.90
Purchase #3	$239.30	10.570%	$264.594	$264.59	$264.60	$264.60
Purchase #4	$86.50	5.627%	$91.3674	$91.37	$91.35	$91.40
Purchase #5	$21.85	13.472%	$24.7936	$24.79	$24.80	$24.80
Purchase #6	$81.70	9.125%	$89.1551	$89.16	$89.15	$89.20
Purchase #7	$134.34	6.227%	$142.7054	$142.71	$142.70	$142.70
7 purchase totals =	$829.64		$899.1253	$899.13	$899.10	$899.20