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	$13.47	3.306%	$13.9153	$13.92	$13.90	$13.90
Purchase #2	$164.86	4.409%	$172.1287	$172.13	$172.15	$172.10
Purchase #3	$102.43	9.637%	$112.3012	$112.30	$112.30	$112.30
Purchase #4	$169.39	11.268%	$188.4769	$188.48	$188.50	$188.50
Purchase #5	$136.69	10.770%	$151.4115	$151.41	$151.40	$151.40
Purchase #6	$200.37	7.839%	$216.077	$216.08	$216.10	$216.10
Purchase #7	$66.32	10.253%	$73.1198	$73.12	$73.10	$73.10
7 purchase totals =	$853.53		$927.4304	$927.44	$927.45	$927.40