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	$232.63	10.191%	$256.3373	$256.34	$256.35	$256.30
Purchase #2	$218.79	13.741%	$248.8539	$248.85	$248.85	$248.90
Purchase #3	$226.38	3.831%	$235.0526	$235.05	$235.05	$235.10
Purchase #4	$182.54	3.196%	$188.374	$188.37	$188.35	$188.40
Purchase #5	$30.48	6.244%	$32.3832	$32.38	$32.40	$32.40
Purchase #6	$181.54	9.769%	$199.2746	$199.27	$199.25	$199.30
Purchase #7	$33.93	7.794%	$36.5745	$36.57	$36.55	$36.60
7 purchase totals =	$1,106.29		$1,196.8501	$1,196.83	$1,196.80	$1,197.00