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	$100.52	4.539%	$105.0826	$105.08	$105.10	$105.10
Purchase #2	$150.63	7.522%	$161.9604	$161.96	$161.95	$162.00
Purchase #3	$69.80	9.586%	$76.491	$76.49	$76.50	$76.50
Purchase #4	$40.42	6.221%	$42.9345	$42.93	$42.95	$42.90
Purchase #5	$111.62	7.176%	$119.6299	$119.63	$119.65	$119.60
Purchase #6	$78.52	13.259%	$88.931	$88.93	$88.95	$88.90
Purchase #7	$102.38	9.378%	$111.9812	$111.98	$112.00	$112.00
7 purchase totals =	$653.89		$707.0106	$707.00	$707.10	$707.00