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	$126.48	4.290%	$131.906	$131.91	$131.90	$131.90
Purchase #2	$217.64	9.710%	$238.7728	$238.77	$238.75	$238.80
Purchase #3	$31.80	7.522%	$34.192	$34.19	$34.20	$34.20
Purchase #4	$41.75	5.379%	$43.9957	$44.00	$44.00	$44.00
Purchase #5	$171.31	11.778%	$191.4869	$191.49	$191.50	$191.50
Purchase #6	$82.65	11.144%	$91.8605	$91.86	$91.85	$91.90
Purchase #7	$30.75	11.499%	$34.2859	$34.29	$34.30	$34.30
7 purchase totals =	$702.38		$766.4998	$766.51	$766.50	$766.60