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	$218.54	6.862%	$233.5362	$233.54	$233.55	$233.50
Purchase #2	$201.60	11.218%	$224.2155	$224.22	$224.20	$224.20
Purchase #3	$50.81	8.474%	$55.1156	$55.12	$55.10	$55.10
Purchase #4	$216.72	6.718%	$231.2792	$231.28	$231.30	$231.30
Purchase #5	$247.67	13.238%	$280.4566	$280.46	$280.45	$280.50
Purchase #6	$230.96	12.610%	$260.0841	$260.08	$260.10	$260.10
Purchase #7	$104.72	4.529%	$109.4628	$109.46	$109.45	$109.50
7 purchase totals =	$1,271.02		$1,394.1500	$1,394.16	$1,394.15	$1,394.20