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	$118.50	12.326%	$133.1063	$133.11	$133.10	$133.10
Purchase #2	$192.39	8.274%	$208.3083	$208.31	$208.30	$208.30
Purchase #3	$187.99	9.723%	$206.2683	$206.27	$206.25	$206.30
Purchase #4	$97.51	3.183%	$100.6137	$100.61	$100.60	$100.60
Purchase #5	$171.54	5.513%	$180.997	$181.00	$181.00	$181.00
Purchase #6	$171.88	10.600%	$190.0993	$190.10	$190.10	$190.10
Purchase #7	$49.57	11.223%	$55.1332	$55.13	$55.15	$55.10
7 purchase totals =	$989.38		$1,074.5261	$1,074.53	$1,074.50	$1,074.50