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	$156.79	11.793%	$175.2802	$175.28	$175.30	$175.30
Purchase #2	$237.64	12.168%	$266.556	$266.56	$266.55	$266.60
Purchase #3	$7.26	8.701%	$7.8917	$7.89	$7.90	$7.90
Purchase #4	$179.26	11.807%	$200.4252	$200.43	$200.45	$200.40
Purchase #5	$62.83	6.428%	$66.8687	$66.87	$66.85	$66.90
Purchase #6	$85.56	10.799%	$94.7996	$94.80	$94.80	$94.80
Purchase #7	$249.40	9.868%	$274.0108	$274.01	$274.00	$274.00
7 purchase totals =	$978.74		$1,085.8322	$1,085.84	$1,085.85	$1,085.90