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	$53.27	3.461%	$55.1137	$55.11	$55.10	$55.10
Purchase #2	$10.64	8.497%	$11.5441	$11.54	$11.55	$11.50
Purchase #3	$86.79	3.826%	$90.1106	$90.11	$90.10	$90.10
Purchase #4	$149.60	13.126%	$169.2365	$169.24	$169.25	$169.20
Purchase #5	$102.67	3.709%	$106.478	$106.48	$106.50	$106.50
Purchase #6	$64.78	10.338%	$71.477	$71.48	$71.50	$71.50
Purchase #7	$64.94	3.611%	$67.285	$67.29	$67.30	$67.30
7 purchase totals =	$532.69		$571.2449	$571.25	$571.30	$571.20