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	$152.41	8.847%	$165.8937	$165.89	$165.90	$165.90
Purchase #2	$133.32	3.490%	$137.9729	$137.97	$137.95	$138.00
Purchase #3	$86.51	13.302%	$98.0176	$98.02	$98.00	$98.00
Purchase #4	$201.34	7.355%	$216.1486	$216.15	$216.15	$216.10
Purchase #5	$160.49	5.626%	$169.5192	$169.52	$169.50	$169.50
Purchase #6	$157.93	7.341%	$169.5236	$169.52	$169.50	$169.50
Purchase #7	$199.89	8.274%	$216.4289	$216.43	$216.45	$216.40
7 purchase totals =	$1,091.89		$1,173.5045	$1,173.50	$1,173.45	$1,173.40