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	$33.63	12.609%	$37.8704	$37.87	$37.85	$37.90
Purchase #2	$127.59	13.269%	$144.5199	$144.52	$144.50	$144.50
Purchase #3	$163.78	5.154%	$172.2212	$172.22	$172.20	$172.20
Purchase #4	$229.76	6.112%	$243.8029	$243.80	$243.80	$243.80
Purchase #5	$179.89	6.744%	$192.0218	$192.02	$192.00	$192.00
Purchase #6	$196.90	6.632%	$209.9584	$209.96	$209.95	$210.00
Purchase #7	$85.41	12.228%	$95.8539	$95.85	$95.85	$95.90
7 purchase totals =	$1,016.96		$1,096.2485	$1,096.24	$1,096.15	$1,096.30