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	$83.76	10.390%	$92.4627	$92.46	$92.45	$92.50
Purchase #2	$128.32	9.767%	$140.853	$140.85	$140.85	$140.90
Purchase #3	$136.37	8.343%	$147.7473	$147.75	$147.75	$147.70
Purchase #4	$168.89	10.396%	$186.4478	$186.45	$186.45	$186.40
Purchase #5	$65.90	10.104%	$72.5585	$72.56	$72.55	$72.60
Purchase #6	$37.43	4.302%	$39.0402	$39.04	$39.05	$39.00
Purchase #7	$152.44	11.454%	$169.9005	$169.90	$169.90	$169.90
7 purchase totals =	$773.11		$849.0100	$849.01	$849.00	$849.00