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	$215.52	13.712%	$245.0721	$245.07	$245.05	$245.10
Purchase #2	$236.28	9.776%	$259.3787	$259.38	$259.40	$259.40
Purchase #3	$215.60	11.666%	$240.7519	$240.75	$240.75	$240.80
Purchase #4	$40.78	3.812%	$42.3345	$42.33	$42.35	$42.30
Purchase #5	$43.58	8.802%	$47.4159	$47.42	$47.40	$47.40
Purchase #6	$89.57	9.215%	$97.8239	$97.82	$97.80	$97.80
Purchase #7	$29.68	12.841%	$33.4912	$33.49	$33.50	$33.50
7 purchase totals =	$871.01		$966.2682	$966.26	$966.25	$966.30