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	$229.29	11.392%	$255.4107	$255.41	$255.40	$255.40
Purchase #2	$65.45	11.373%	$72.8936	$72.89	$72.90	$72.90
Purchase #3	$50.63	10.449%	$55.9203	$55.92	$55.90	$55.90
Purchase #4	$87.28	6.332%	$92.8066	$92.81	$92.80	$92.80
Purchase #5	$79.56	10.186%	$87.664	$87.66	$87.65	$87.70
Purchase #6	$172.52	10.140%	$190.0135	$190.01	$190.00	$190.00
Purchase #7	$249.63	10.693%	$276.3229	$276.32	$276.30	$276.30
7 purchase totals =	$934.36		$1,031.0316	$1,031.02	$1,030.95	$1,031.00