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	$144.36	13.650%	$164.0651	$164.07	$164.05	$164.10
Purchase #2	$94.36	9.785%	$103.5931	$103.59	$103.60	$103.60
Purchase #3	$60.95	11.388%	$67.891	$67.89	$67.90	$67.90
Purchase #4	$53.52	6.358%	$56.9228	$56.92	$56.90	$56.90
Purchase #5	$195.94	10.702%	$216.9095	$216.91	$216.90	$216.90
Purchase #6	$230.91	13.780%	$262.7294	$262.73	$262.75	$262.70
Purchase #7	$178.47	13.139%	$201.9192	$201.92	$201.90	$201.90
7 purchase totals =	$958.51		$1,074.0301	$1,074.03	$1,074.00	$1,074.00