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	$151.32	11.220%	$168.2981	$168.30	$168.30	$168.30
Purchase #2	$114.50	11.218%	$127.3446	$127.34	$127.35	$127.30
Purchase #3	$245.45	10.428%	$271.0455	$271.05	$271.05	$271.00
Purchase #4	$164.81	13.777%	$187.5159	$187.52	$187.50	$187.50
Purchase #5	$51.78	12.105%	$58.048	$58.05	$58.05	$58.00
Purchase #6	$55.36	8.139%	$59.8658	$59.87	$59.85	$59.90
Purchase #7	$114.83	10.419%	$126.7941	$126.79	$126.80	$126.80
7 purchase totals =	$898.05		$998.9120	$998.92	$998.90	$998.80