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	$182.87	3.729%	$189.6892	$189.69	$189.70	$189.70
Purchase #2	$63.41	12.653%	$71.4333	$71.43	$71.45	$71.40
Purchase #3	$235.90	5.586%	$249.0774	$249.08	$249.10	$249.10
Purchase #4	$179.49	7.268%	$192.5353	$192.54	$192.55	$192.50
Purchase #5	$35.76	12.418%	$40.2007	$40.20	$40.20	$40.20
Purchase #6	$38.47	7.706%	$41.4345	$41.43	$41.45	$41.40
Purchase #7	$245.57	7.738%	$264.5722	$264.57	$264.55	$264.60
7 purchase totals =	$981.47		$1,048.9426	$1,048.94	$1,049.00	$1,048.90