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	$165.59	12.548%	$186.3682	$186.37	$186.35	$186.40
Purchase #2	$127.63	11.218%	$141.9475	$141.95	$141.95	$141.90
Purchase #3	$155.30	11.387%	$172.984	$172.98	$173.00	$173.00
Purchase #4	$95.94	3.828%	$99.6126	$99.61	$99.60	$99.60
Purchase #5	$218.89	5.599%	$231.1457	$231.15	$231.15	$231.10
Purchase #6	$238.33	3.849%	$247.5033	$247.50	$247.50	$247.50
Purchase #7	$27.83	5.598%	$29.3879	$29.39	$29.40	$29.40
7 purchase totals =	$1,029.51		$1,108.9492	$1,108.95	$1,108.95	$1,108.90