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	$175.25	8.856%	$190.7701	$190.77	$190.75	$190.80
Purchase #2	$230.73	8.148%	$249.5299	$249.53	$249.55	$249.50
Purchase #3	$213.35	3.495%	$220.8066	$220.81	$220.80	$220.80
Purchase #4	$168.64	7.750%	$181.7096	$181.71	$181.70	$181.70
Purchase #5	$31.51	13.774%	$35.8502	$35.85	$35.85	$35.90
Purchase #6	$43.48	12.646%	$48.9785	$48.98	$49.00	$49.00
Purchase #7	$138.50	10.667%	$153.2738	$153.27	$153.25	$153.30
7 purchase totals =	$1,001.46		$1,080.9187	$1,080.92	$1,080.90	$1,081.00