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	$77.91	7.659%	$83.8771	$83.88	$83.90	$83.90
Purchase #2	$61.41	11.284%	$68.3395	$68.34	$68.35	$68.30
Purchase #3	$118.30	7.767%	$127.4884	$127.49	$127.50	$127.50
Purchase #4	$176.64	13.758%	$200.9421	$200.94	$200.95	$200.90
Purchase #5	$83.88	3.587%	$86.8888	$86.89	$86.90	$86.90
Purchase #6	$181.86	8.863%	$197.9783	$197.98	$198.00	$198.00
Purchase #7	$234.96	4.285%	$245.028	$245.03	$245.05	$245.00
7 purchase totals =	$934.96		$1,010.5422	$1,010.55	$1,010.65	$1,010.50