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	$239.68	5.686%	$253.3082	$253.31	$253.30	$253.30
Purchase #2	$247.55	13.482%	$280.9247	$280.92	$280.90	$280.90
Purchase #3	$46.40	6.316%	$49.3306	$49.33	$49.35	$49.30
Purchase #4	$208.85	7.379%	$224.261	$224.26	$224.25	$224.30
Purchase #5	$244.55	7.643%	$263.241	$263.24	$263.25	$263.20
Purchase #6	$87.35	3.348%	$90.2745	$90.27	$90.25	$90.30
Purchase #7	$6.33	10.648%	$7.004	$7.00	$7.00	$7.00
7 purchase totals =	$1,080.71		$1,168.3440	$1,168.33	$1,168.30	$1,168.30