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	$134.71	8.320%	$145.9179	$145.92	$145.90	$145.90
Purchase #2	$225.47	12.601%	$253.8815	$253.88	$253.90	$253.90
Purchase #3	$24.25	3.322%	$25.0556	$25.06	$25.05	$25.10
Purchase #4	$125.89	12.592%	$141.7421	$141.74	$141.75	$141.70
Purchase #5	$98.80	4.585%	$103.33	$103.33	$103.35	$103.30
Purchase #6	$42.75	8.622%	$46.4359	$46.44	$46.45	$46.40
Purchase #7	$192.50	10.387%	$212.495	$212.50	$212.50	$212.50
7 purchase totals =	$844.37		$928.8580	$928.87	$928.90	$928.80