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	$134.80	8.139%	$145.7714	$145.77	$145.75	$145.80
Purchase #2	$96.38	3.644%	$99.8921	$99.89	$99.90	$99.90
Purchase #3	$88.56	4.695%	$92.7179	$92.72	$92.70	$92.70
Purchase #4	$112.95	11.735%	$126.2047	$126.20	$126.20	$126.20
Purchase #5	$29.33	10.476%	$32.4026	$32.40	$32.40	$32.40
Purchase #6	$136.81	7.807%	$147.4908	$147.49	$147.50	$147.50
Purchase #7	$205.85	13.622%	$233.8909	$233.89	$233.90	$233.90
7 purchase totals =	$804.68		$878.3704	$878.36	$878.35	$878.40