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	$34.88	5.497%	$36.7974	$36.80	$36.80	$36.80
Purchase #2	$196.32	10.507%	$216.9473	$216.95	$216.95	$216.90
Purchase #3	$51.44	10.853%	$57.0228	$57.02	$57.00	$57.00
Purchase #4	$99.36	11.763%	$111.0477	$111.05	$111.05	$111.00
Purchase #5	$80.35	7.206%	$86.14	$86.14	$86.15	$86.10
Purchase #6	$135.81	11.118%	$150.9094	$150.91	$150.90	$150.90
Purchase #7	$158.28	13.417%	$179.5164	$179.52	$179.50	$179.50
7 purchase totals =	$756.44		$838.3810	$838.39	$838.35	$838.20