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	$136.35	10.726%	$150.9749	$150.97	$150.95	$151.00
Purchase #2	$198.99	13.746%	$226.3432	$226.34	$226.35	$226.30
Purchase #3	$126.82	11.573%	$141.4969	$141.50	$141.50	$141.50
Purchase #4	$69.47	4.806%	$72.8087	$72.81	$72.80	$72.80
Purchase #5	$137.78	7.701%	$148.3904	$148.39	$148.40	$148.40
Purchase #6	$33.52	10.368%	$36.9954	$37.00	$37.00	$37.00
Purchase #7	$236.77	9.590%	$259.4762	$259.48	$259.50	$259.50
7 purchase totals =	$939.70		$1,036.4857	$1,036.49	$1,036.50	$1,036.50