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	$204.90	9.625%	$224.6216	$224.62	$224.60	$224.60
Purchase #2	$206.66	7.714%	$222.6018	$222.60	$222.60	$222.60
Purchase #3	$72.69	7.677%	$78.2704	$78.27	$78.25	$78.30
Purchase #4	$144.61	5.134%	$152.0343	$152.03	$152.05	$152.00
Purchase #5	$172.44	7.759%	$185.8196	$185.82	$185.80	$185.80
Purchase #6	$233.75	10.802%	$258.9997	$259.00	$259.00	$259.00
Purchase #7	$185.25	8.271%	$200.572	$200.57	$200.55	$200.60
7 purchase totals =	$1,220.30		$1,322.9194	$1,322.91	$1,322.85	$1,322.90