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	$52.90	11.606%	$59.0396	$59.04	$59.05	$59.00
Purchase #2	$98.77	5.402%	$104.1056	$104.11	$104.10	$104.10
Purchase #3	$34.28	3.427%	$35.4548	$35.45	$35.45	$35.50
Purchase #4	$181.48	8.394%	$196.7134	$196.71	$196.70	$196.70
Purchase #5	$25.34	5.693%	$26.7826	$26.78	$26.80	$26.80
Purchase #6	$12.26	13.338%	$13.8952	$13.90	$13.90	$13.90
Purchase #7	$28.92	13.525%	$32.8314	$32.83	$32.85	$32.80
7 purchase totals =	$433.95		$468.8226	$468.82	$468.85	$468.80