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	$20.60	10.261%	$22.7138	$22.71	$22.70	$22.70
Purchase #2	$29.33	11.283%	$32.6393	$32.64	$32.65	$32.60
Purchase #3	$86.54	7.377%	$92.9241	$92.92	$92.90	$92.90
Purchase #4	$76.78	5.302%	$80.8509	$80.85	$80.85	$80.90
Purchase #5	$20.39	10.402%	$22.511	$22.51	$22.50	$22.50
Purchase #6	$137.84	3.836%	$143.1275	$143.13	$143.15	$143.10
Purchase #7	$79.85	12.756%	$90.0357	$90.04	$90.05	$90.00
7 purchase totals =	$451.33		$484.8023	$484.80	$484.80	$484.70