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	$126.98	11.188%	$141.1865	$141.19	$141.20	$141.20
Purchase #2	$149.55	13.230%	$169.3355	$169.34	$169.35	$169.30
Purchase #3	$127.59	12.704%	$143.799	$143.80	$143.80	$143.80
Purchase #4	$182.59	5.196%	$192.0774	$192.08	$192.10	$192.10
Purchase #5	$241.33	6.656%	$257.3929	$257.39	$257.40	$257.40
Purchase #6	$81.53	9.669%	$89.4131	$89.41	$89.40	$89.40
Purchase #7	$138.48	10.427%	$152.9193	$152.92	$152.90	$152.90
7 purchase totals =	$1,048.05		$1,146.1237	$1,146.13	$1,146.15	$1,146.10