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	$107.98	4.824%	$113.189	$113.19	$113.20	$113.20
Purchase #2	$103.50	7.332%	$111.0886	$111.09	$111.10	$111.10
Purchase #3	$59.36	5.254%	$62.4788	$62.48	$62.50	$62.50
Purchase #4	$147.46	9.634%	$161.6663	$161.67	$161.65	$161.70
Purchase #5	$93.33	10.569%	$103.194	$103.19	$103.20	$103.20
Purchase #6	$122.81	10.860%	$136.1472	$136.15	$136.15	$136.10
Purchase #7	$68.89	5.720%	$72.8305	$72.83	$72.85	$72.80
7 purchase totals =	$703.33		$760.5944	$760.60	$760.65	$760.60