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	$156.33	10.626%	$172.9416	$172.94	$172.95	$172.90
Purchase #2	$109.48	12.345%	$122.9953	$123.00	$123.00	$123.00
Purchase #3	$170.84	13.231%	$193.4438	$193.44	$193.45	$193.40
Purchase #4	$85.34	12.412%	$95.9324	$95.93	$95.95	$95.90
Purchase #5	$150.30	4.863%	$157.6091	$157.61	$157.60	$157.60
Purchase #6	$161.89	3.570%	$167.6695	$167.67	$167.65	$167.70
Purchase #7	$239.27	12.382%	$268.8964	$268.90	$268.90	$268.90
7 purchase totals =	$1,073.45		$1,179.4881	$1,179.49	$1,179.50	$1,179.40