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	$211.78	7.729%	$228.1485	$228.15	$228.15	$228.10
Purchase #2	$199.86	5.823%	$211.4978	$211.50	$211.50	$211.50
Purchase #3	$181.47	10.401%	$200.3447	$200.34	$200.35	$200.30
Purchase #4	$15.87	13.731%	$18.0491	$18.05	$18.05	$18.00
Purchase #5	$145.47	5.758%	$153.8462	$153.85	$153.85	$153.80
Purchase #6	$209.39	13.222%	$237.0755	$237.08	$237.10	$237.10
Purchase #7	$78.26	13.812%	$89.0693	$89.07	$89.05	$89.10
7 purchase totals =	$1,042.10		$1,138.0311	$1,138.04	$1,138.05	$1,137.90