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	$57.77	8.767%	$62.8347	$62.83	$62.85	$62.80
Purchase #2	$72.82	7.314%	$78.1461	$78.15	$78.15	$78.10
Purchase #3	$102.90	5.828%	$108.897	$108.90	$108.90	$108.90
Purchase #4	$18.74	7.615%	$20.1671	$20.17	$20.15	$20.20
Purchase #5	$199.50	3.615%	$206.7119	$206.71	$206.70	$206.70
Purchase #6	$199.77	7.666%	$215.0844	$215.08	$215.10	$215.10
Purchase #7	$232.55	11.631%	$259.5979	$259.60	$259.60	$259.60
7 purchase totals =	$884.05		$951.4391	$951.44	$951.45	$951.40