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	$186.79	5.217%	$196.5348	$196.53	$196.55	$196.50
Purchase #2	$132.36	11.845%	$148.038	$148.04	$148.05	$148.00
Purchase #3	$59.65	7.377%	$64.0504	$64.05	$64.05	$64.10
Purchase #4	$55.76	12.604%	$62.788	$62.79	$62.80	$62.80
Purchase #5	$48.54	11.660%	$54.1998	$54.20	$54.20	$54.20
Purchase #6	$94.50	11.443%	$105.3136	$105.31	$105.30	$105.30
Purchase #7	$40.26	10.340%	$44.4229	$44.42	$44.40	$44.40
7 purchase totals =	$617.86		$675.3475	$675.34	$675.35	$675.30