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	$103.68	11.695%	$115.8054	$115.81	$115.80	$115.80
Purchase #2	$141.27	7.272%	$151.5432	$151.54	$151.55	$151.50
Purchase #3	$99.79	12.733%	$112.4963	$112.50	$112.50	$112.50
Purchase #4	$159.89	8.626%	$173.6821	$173.68	$173.70	$173.70
Purchase #5	$41.92	9.387%	$45.855	$45.86	$45.85	$45.90
Purchase #6	$77.71	7.644%	$83.6502	$83.65	$83.65	$83.70
Purchase #7	$124.86	7.181%	$133.8262	$133.83	$133.85	$133.80
7 purchase totals =	$749.12		$816.8584	$816.87	$816.90	$816.90