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	$153.61	10.415%	$169.6085	$169.61	$169.60	$169.60
Purchase #2	$78.46	4.514%	$82.0017	$82.00	$82.00	$82.00
Purchase #3	$147.82	8.845%	$160.8947	$160.89	$160.90	$160.90
Purchase #4	$125.71	12.873%	$141.8926	$141.89	$141.90	$141.90
Purchase #5	$90.82	12.460%	$102.1362	$102.14	$102.15	$102.10
Purchase #6	$10.41	6.299%	$11.0657	$11.07	$11.05	$11.10
Purchase #7	$8.74	8.454%	$9.4789	$9.48	$9.50	$9.50
7 purchase totals =	$615.57		$677.0783	$677.08	$677.10	$677.10