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	$195.53	5.792%	$206.8551	$206.86	$206.85	$206.90
Purchase #2	$134.34	12.666%	$151.3555	$151.36	$151.35	$151.40
Purchase #3	$87.71	13.158%	$99.2509	$99.25	$99.25	$99.30
Purchase #4	$241.97	13.345%	$274.2609	$274.26	$274.25	$274.30
Purchase #5	$133.53	13.484%	$151.5352	$151.54	$151.55	$151.50
Purchase #6	$36.67	13.340%	$41.5618	$41.56	$41.55	$41.60
Purchase #7	$86.68	9.438%	$94.8609	$94.86	$94.85	$94.90
7 purchase totals =	$916.43		$1,019.6803	$1,019.69	$1,019.65	$1,019.90