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	$222.31	12.825%	$250.8213	$250.82	$250.80	$250.80
Purchase #2	$215.88	7.668%	$232.4337	$232.43	$232.45	$232.40
Purchase #3	$146.69	6.786%	$156.6444	$156.64	$156.65	$156.60
Purchase #4	$135.91	12.213%	$152.5087	$152.51	$152.50	$152.50
Purchase #5	$136.92	5.604%	$144.593	$144.59	$144.60	$144.60
Purchase #6	$56.45	8.678%	$61.3487	$61.35	$61.35	$61.30
Purchase #7	$35.78	10.379%	$39.4936	$39.49	$39.50	$39.50
7 purchase totals =	$949.94		$1,037.8434	$1,037.83	$1,037.85	$1,037.70