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	$186.40	10.302%	$205.6029	$205.60	$205.60	$205.60
Purchase #2	$48.93	8.861%	$53.2657	$53.27	$53.25	$53.30
Purchase #3	$250.59	9.236%	$273.7345	$273.73	$273.75	$273.70
Purchase #4	$223.42	8.484%	$242.375	$242.38	$242.40	$242.40
Purchase #5	$127.91	5.274%	$134.656	$134.66	$134.65	$134.70
Purchase #6	$116.88	8.816%	$127.1841	$127.18	$127.20	$127.20
Purchase #7	$87.73	8.265%	$94.9809	$94.98	$95.00	$95.00
7 purchase totals =	$1,041.86		$1,131.7991	$1,131.80	$1,131.85	$1,131.90