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	$202.66	7.347%	$217.5494	$217.55	$217.55	$217.50
Purchase #2	$226.43	3.264%	$233.8207	$233.82	$233.80	$233.80
Purchase #3	$221.40	12.623%	$249.3473	$249.35	$249.35	$249.30
Purchase #4	$33.40	11.691%	$37.3048	$37.30	$37.30	$37.30
Purchase #5	$80.57	9.713%	$88.3958	$88.40	$88.40	$88.40
Purchase #6	$112.28	13.515%	$127.4546	$127.45	$127.45	$127.50
Purchase #7	$68.49	5.734%	$72.4172	$72.42	$72.40	$72.40
7 purchase totals =	$945.23		$1,026.2898	$1,026.29	$1,026.25	$1,026.20