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	$56.88	4.526%	$59.4544	$59.45	$59.45	$59.50
Purchase #2	$175.92	4.674%	$184.1425	$184.14	$184.15	$184.10
Purchase #3	$161.98	3.649%	$167.8907	$167.89	$167.90	$167.90
Purchase #4	$135.72	5.400%	$143.0489	$143.05	$143.05	$143.00
Purchase #5	$58.71	11.450%	$65.4323	$65.43	$65.45	$65.40
Purchase #6	$126.46	5.111%	$132.9234	$132.92	$132.90	$132.90
Purchase #7	$47.45	8.499%	$51.4828	$51.48	$51.50	$51.50
7 purchase totals =	$763.12		$804.3750	$804.36	$804.40	$804.30