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	$172.67	7.218%	$185.1333	$185.13	$185.15	$185.10
Purchase #2	$53.38	8.545%	$57.9413	$57.94	$57.95	$57.90
Purchase #3	$12.36	3.386%	$12.7785	$12.78	$12.80	$12.80
Purchase #4	$45.95	11.747%	$51.3477	$51.35	$51.35	$51.30
Purchase #5	$72.49	8.650%	$78.7604	$78.76	$78.75	$78.80
Purchase #6	$175.75	11.412%	$195.8066	$195.81	$195.80	$195.80
Purchase #7	$181.89	5.832%	$192.4978	$192.50	$192.50	$192.50
7 purchase totals =	$714.49		$774.2656	$774.27	$774.30	$774.20