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	$249.43	13.462%	$283.0083	$283.01	$283.00	$283.00
Purchase #2	$192.69	13.430%	$218.5683	$218.57	$218.55	$218.60
Purchase #3	$188.33	5.713%	$199.0893	$199.09	$199.10	$199.10
Purchase #4	$196.85	7.611%	$211.8323	$211.83	$211.85	$211.80
Purchase #5	$67.73	4.586%	$70.8361	$70.84	$70.85	$70.80
Purchase #6	$90.42	8.256%	$97.8851	$97.89	$97.90	$97.90
Purchase #7	$33.52	10.702%	$37.1073	$37.11	$37.10	$37.10
7 purchase totals =	$1,018.97		$1,118.3267	$1,118.34	$1,118.35	$1,118.30