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	$109.29	8.594%	$118.6824	$118.68	$118.70	$118.70
Purchase #2	$206.68	10.803%	$229.0076	$229.01	$229.00	$229.00
Purchase #3	$123.63	7.664%	$133.105	$133.11	$133.10	$133.10
Purchase #4	$206.50	7.791%	$222.5884	$222.59	$222.60	$222.60
Purchase #5	$89.82	13.763%	$102.1819	$102.18	$102.20	$102.20
Purchase #6	$61.72	9.630%	$67.6636	$67.66	$67.65	$67.70
Purchase #7	$164.57	4.716%	$172.3311	$172.33	$172.35	$172.30
7 purchase totals =	$962.21		$1,045.5600	$1,045.56	$1,045.60	$1,045.60