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	$147.38	6.220%	$156.547	$156.55	$156.55	$156.50
Purchase #2	$77.60	10.442%	$85.703	$85.70	$85.70	$85.70
Purchase #3	$89.50	11.296%	$99.6099	$99.61	$99.60	$99.60
Purchase #4	$107.34	5.169%	$112.8884	$112.89	$112.90	$112.90
Purchase #5	$82.41	9.718%	$90.4186	$90.42	$90.40	$90.40
Purchase #6	$70.31	10.800%	$77.9035	$77.90	$77.90	$77.90
Purchase #7	$78.39	5.633%	$82.8057	$82.81	$82.80	$82.80
7 purchase totals =	$652.93		$705.8761	$705.88	$705.85	$705.80