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	$203.84	10.360%	$224.9578	$224.96	$224.95	$225.00
Purchase #2	$114.32	11.420%	$127.3753	$127.38	$127.40	$127.40
Purchase #3	$120.71	4.312%	$125.915	$125.92	$125.90	$125.90
Purchase #4	$10.26	3.159%	$10.5841	$10.58	$10.60	$10.60
Purchase #5	$141.72	10.262%	$156.2633	$156.26	$156.25	$156.30
Purchase #6	$69.67	3.590%	$72.1712	$72.17	$72.15	$72.20
Purchase #7	$152.44	13.853%	$173.5575	$173.56	$173.55	$173.60
7 purchase totals =	$812.96		$890.8242	$890.83	$890.80	$891.00