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	$211.62	7.454%	$227.3942	$227.39	$227.40	$227.40
Purchase #2	$10.59	6.550%	$11.2836	$11.28	$11.30	$11.30
Purchase #3	$180.55	10.706%	$199.8797	$199.88	$199.90	$199.90
Purchase #4	$72.98	6.796%	$77.9397	$77.94	$77.95	$77.90
Purchase #5	$105.63	13.630%	$120.0274	$120.03	$120.05	$120.00
Purchase #6	$237.51	6.770%	$253.5894	$253.59	$253.60	$253.60
Purchase #7	$82.49	8.598%	$89.5825	$89.58	$89.60	$89.60
7 purchase totals =	$901.37		$979.6965	$979.69	$979.80	$979.70