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	$174.67	12.139%	$195.8732	$195.87	$195.85	$195.90
Purchase #2	$137.80	3.787%	$143.0185	$143.02	$143.00	$143.00
Purchase #3	$85.82	11.651%	$95.8189	$95.82	$95.80	$95.80
Purchase #4	$6.84	9.563%	$7.4941	$7.49	$7.50	$7.50
Purchase #5	$33.34	3.859%	$34.6266	$34.63	$34.65	$34.60
Purchase #6	$80.87	11.325%	$90.0285	$90.03	$90.05	$90.00
Purchase #7	$194.88	12.112%	$218.4839	$218.48	$218.50	$218.50
7 purchase totals =	$714.22		$785.3437	$785.34	$785.35	$785.30