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	$137.58	13.816%	$156.5881	$156.59	$156.60	$156.60
Purchase #2	$92.48	4.373%	$96.5242	$96.52	$96.50	$96.50
Purchase #3	$191.53	11.287%	$213.148	$213.15	$213.15	$213.10
Purchase #4	$95.91	4.396%	$100.1262	$100.13	$100.15	$100.10
Purchase #5	$52.70	12.506%	$59.2907	$59.29	$59.30	$59.30
Purchase #6	$167.70	11.632%	$187.2069	$187.21	$187.20	$187.20
Purchase #7	$224.91	8.484%	$243.9914	$243.99	$244.00	$244.00
7 purchase totals =	$962.81		$1,056.8755	$1,056.88	$1,056.90	$1,056.80