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	$73.41	13.591%	$83.3872	$83.39	$83.40	$83.40
Purchase #2	$187.49	7.199%	$200.9874	$200.99	$201.00	$201.00
Purchase #3	$153.34	4.234%	$159.8324	$159.83	$159.85	$159.80
Purchase #4	$131.85	9.116%	$143.8694	$143.87	$143.85	$143.90
Purchase #5	$107.37	8.294%	$116.2753	$116.28	$116.30	$116.30
Purchase #6	$54.45	9.428%	$59.5835	$59.58	$59.60	$59.60
Purchase #7	$197.61	9.454%	$216.292	$216.29	$216.30	$216.30
7 purchase totals =	$905.52		$980.2272	$980.23	$980.30	$980.30