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	$143.59	3.660%	$148.8454	$148.85	$148.85	$148.80
Purchase #2	$214.25	7.124%	$229.5132	$229.51	$229.50	$229.50
Purchase #3	$39.60	6.609%	$42.2172	$42.22	$42.20	$42.20
Purchase #4	$17.54	4.255%	$18.2863	$18.29	$18.30	$18.30
Purchase #5	$94.80	5.666%	$100.1714	$100.17	$100.15	$100.20
Purchase #6	$205.96	6.838%	$220.0435	$220.04	$220.05	$220.00
Purchase #7	$62.95	7.789%	$67.8532	$67.85	$67.85	$67.90
7 purchase totals =	$778.69		$826.9302	$826.93	$826.90	$826.90