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	$118.53	10.551%	$131.0361	$131.04	$131.05	$131.00
Purchase #2	$238.48	12.551%	$268.4116	$268.41	$268.40	$268.40
Purchase #3	$128.91	6.211%	$136.9166	$136.92	$136.90	$136.90
Purchase #4	$217.87	9.398%	$238.3454	$238.35	$238.35	$238.30
Purchase #5	$66.94	8.742%	$72.7919	$72.79	$72.80	$72.80
Purchase #6	$237.98	4.660%	$249.0699	$249.07	$249.05	$249.10
Purchase #7	$29.82	4.108%	$31.045	$31.05	$31.05	$31.00
7 purchase totals =	$1,038.53		$1,127.6165	$1,127.63	$1,127.60	$1,127.50