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	$189.54	13.383%	$214.9061	$214.91	$214.90	$214.90
Purchase #2	$78.47	8.742%	$85.3298	$85.33	$85.35	$85.30
Purchase #3	$143.83	6.717%	$153.4911	$153.49	$153.50	$153.50
Purchase #4	$220.89	12.785%	$249.1308	$249.13	$249.15	$249.10
Purchase #5	$250.97	8.712%	$272.8345	$272.83	$272.85	$272.80
Purchase #6	$59.47	5.666%	$62.8396	$62.84	$62.85	$62.80
Purchase #7	$245.68	4.544%	$256.8437	$256.84	$256.85	$256.80
7 purchase totals =	$1,188.85		$1,295.3756	$1,295.37	$1,295.45	$1,295.20