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	$132.48	6.320%	$140.8527	$140.85	$140.85	$140.90
Purchase #2	$103.96	7.691%	$111.9556	$111.96	$111.95	$112.00
Purchase #3	$51.77	10.835%	$57.3793	$57.38	$57.40	$57.40
Purchase #4	$194.32	11.364%	$216.4025	$216.40	$216.40	$216.40
Purchase #5	$177.83	6.349%	$189.1204	$189.12	$189.10	$189.10
Purchase #6	$25.57	5.627%	$27.0088	$27.01	$27.00	$27.00
Purchase #7	$96.94	4.752%	$101.5466	$101.55	$101.55	$101.50
7 purchase totals =	$782.87		$844.2659	$844.27	$844.25	$844.30