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	$199.63	6.720%	$213.0451	$213.05	$213.05	$213.00
Purchase #2	$93.76	3.336%	$96.8878	$96.89	$96.90	$96.90
Purchase #3	$186.38	12.624%	$209.9086	$209.91	$209.90	$209.90
Purchase #4	$226.80	13.218%	$256.7784	$256.78	$256.80	$256.80
Purchase #5	$176.55	11.270%	$196.4472	$196.45	$196.45	$196.40
Purchase #6	$89.32	4.530%	$93.3662	$93.37	$93.35	$93.40
Purchase #7	$44.33	11.873%	$49.5933	$49.59	$49.60	$49.60
7 purchase totals =	$1,016.77		$1,116.0266	$1,116.04	$1,116.05	$1,116.00