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	$136.64	11.861%	$152.8469	$152.85	$152.85	$152.80
Purchase #2	$178.44	5.292%	$187.883	$187.88	$187.90	$187.90
Purchase #3	$140.90	4.492%	$147.2292	$147.23	$147.25	$147.20
Purchase #4	$188.63	9.435%	$206.4272	$206.43	$206.45	$206.40
Purchase #5	$43.37	3.127%	$44.7262	$44.73	$44.75	$44.70
Purchase #6	$6.66	11.671%	$7.4373	$7.44	$7.45	$7.40
Purchase #7	$155.69	10.735%	$172.4033	$172.40	$172.40	$172.40
7 purchase totals =	$850.33		$918.9531	$918.96	$919.05	$918.80