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	$189.67	13.325%	$214.9435	$214.94	$214.95	$214.90
Purchase #2	$214.85	10.302%	$236.9838	$236.98	$237.00	$237.00
Purchase #3	$42.55	6.744%	$45.4196	$45.42	$45.40	$45.40
Purchase #4	$91.56	4.192%	$95.3982	$95.40	$95.40	$95.40
Purchase #5	$241.82	13.482%	$274.4222	$274.42	$274.40	$274.40
Purchase #6	$139.40	12.232%	$156.4514	$156.45	$156.45	$156.50
Purchase #7	$199.69	9.806%	$219.2716	$219.27	$219.25	$219.30
7 purchase totals =	$1,119.54		$1,242.8903	$1,242.88	$1,242.85	$1,242.90