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	$162.76	3.732%	$168.8342	$168.83	$168.85	$168.80
Purchase #2	$161.27	13.151%	$182.4786	$182.48	$182.50	$182.50
Purchase #3	$231.51	6.570%	$246.7202	$246.72	$246.70	$246.70
Purchase #4	$225.83	13.540%	$256.4074	$256.41	$256.40	$256.40
Purchase #5	$63.27	4.597%	$66.1785	$66.18	$66.20	$66.20
Purchase #6	$144.76	4.722%	$151.5956	$151.60	$151.60	$151.60
Purchase #7	$37.32	12.401%	$41.9481	$41.95	$41.95	$41.90
7 purchase totals =	$1,026.72		$1,114.1626	$1,114.17	$1,114.20	$1,114.10