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	$162.46	3.294%	$167.8114	$167.81	$167.80	$167.80
Purchase #2	$10.25	6.194%	$10.8849	$10.88	$10.90	$10.90
Purchase #3	$99.37	12.442%	$111.7336	$111.73	$111.75	$111.70
Purchase #4	$9.76	11.669%	$10.8989	$10.90	$10.90	$10.90
Purchase #5	$57.29	3.548%	$59.3226	$59.32	$59.30	$59.30
Purchase #6	$246.64	3.364%	$254.937	$254.94	$254.95	$254.90
Purchase #7	$213.76	7.830%	$230.4974	$230.50	$230.50	$230.50
7 purchase totals =	$799.53		$846.0858	$846.08	$846.10	$846.00