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	$213.66	11.730%	$238.7223	$238.72	$238.70	$238.70
Purchase #2	$74.83	7.516%	$80.4542	$80.45	$80.45	$80.50
Purchase #3	$161.35	10.336%	$178.0271	$178.03	$178.05	$178.00
Purchase #4	$173.31	7.614%	$186.5058	$186.51	$186.50	$186.50
Purchase #5	$125.98	8.200%	$136.3104	$136.31	$136.30	$136.30
Purchase #6	$100.82	11.756%	$112.6724	$112.67	$112.65	$112.70
Purchase #7	$196.46	7.223%	$210.6503	$210.65	$210.65	$210.70
7 purchase totals =	$1,046.41		$1,143.3425	$1,143.34	$1,143.30	$1,143.40