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	$173.28	7.850%	$186.8825	$186.88	$186.90	$186.90
Purchase #2	$204.29	10.707%	$226.1633	$226.16	$226.15	$226.20
Purchase #3	$12.34	3.860%	$12.8163	$12.82	$12.80	$12.80
Purchase #4	$153.85	5.392%	$162.1456	$162.15	$162.15	$162.10
Purchase #5	$40.67	4.609%	$42.5445	$42.54	$42.55	$42.50
Purchase #6	$86.96	12.160%	$97.5343	$97.53	$97.55	$97.50
Purchase #7	$33.43	11.555%	$37.2928	$37.29	$37.30	$37.30
7 purchase totals =	$704.82		$765.3793	$765.37	$765.40	$765.30