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	$218.78	3.269%	$225.9319	$225.93	$225.95	$225.90
Purchase #2	$107.89	11.616%	$120.4225	$120.42	$120.40	$120.40
Purchase #3	$58.96	6.680%	$62.8985	$62.90	$62.90	$62.90
Purchase #4	$153.92	13.598%	$174.85	$174.85	$174.85	$174.90
Purchase #5	$127.53	12.798%	$143.8513	$143.85	$143.85	$143.90
Purchase #6	$83.36	6.547%	$88.8176	$88.82	$88.80	$88.80
Purchase #7	$167.45	11.331%	$186.4238	$186.42	$186.40	$186.40
7 purchase totals =	$917.89		$1,003.1956	$1,003.19	$1,003.15	$1,003.20