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	$68.54	12.578%	$77.161	$77.16	$77.15	$77.20
Purchase #2	$19.98	3.588%	$20.6969	$20.70	$20.70	$20.70
Purchase #3	$177.27	10.598%	$196.0571	$196.06	$196.05	$196.10
Purchase #4	$207.93	3.102%	$214.38	$214.38	$214.40	$214.40
Purchase #5	$30.55	11.442%	$34.0455	$34.05	$34.05	$34.00
Purchase #6	$70.33	3.714%	$72.9421	$72.94	$72.95	$72.90
Purchase #7	$32.37	8.472%	$35.1124	$35.11	$35.10	$35.10
7 purchase totals =	$606.97		$650.3950	$650.40	$650.40	$650.40