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	$136.75	9.850%	$150.2199	$150.22	$150.20	$150.20
Purchase #2	$222.80	13.183%	$252.1717	$252.17	$252.15	$252.20
Purchase #3	$208.69	5.289%	$219.7276	$219.73	$219.75	$219.70
Purchase #4	$63.46	13.830%	$72.2365	$72.24	$72.25	$72.20
Purchase #5	$164.31	4.702%	$172.0359	$172.04	$172.05	$172.00
Purchase #6	$147.40	13.798%	$167.7383	$167.74	$167.75	$167.70
Purchase #7	$119.51	11.780%	$133.5883	$133.59	$133.60	$133.60
7 purchase totals =	$1,062.92		$1,167.7182	$1,167.73	$1,167.75	$1,167.60