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	$148.38	10.673%	$164.2166	$164.22	$164.20	$164.20
Purchase #2	$241.43	7.480%	$259.489	$259.49	$259.50	$259.50
Purchase #3	$137.34	12.570%	$154.6036	$154.60	$154.60	$154.60
Purchase #4	$196.51	10.379%	$216.9058	$216.91	$216.90	$216.90
Purchase #5	$147.41	3.189%	$152.1109	$152.11	$152.10	$152.10
Purchase #6	$58.66	4.861%	$61.5115	$61.51	$61.50	$61.50
Purchase #7	$136.88	11.756%	$152.9716	$152.97	$152.95	$153.00
7 purchase totals =	$1,066.61		$1,161.8090	$1,161.81	$1,161.75	$1,161.80