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	$147.77	9.742%	$162.1658	$162.17	$162.15	$162.20
Purchase #2	$35.60	7.401%	$38.2348	$38.23	$38.25	$38.20
Purchase #3	$188.95	12.116%	$211.8432	$211.84	$211.85	$211.80
Purchase #4	$103.96	10.443%	$114.8165	$114.82	$114.80	$114.80
Purchase #5	$212.80	13.484%	$241.494	$241.49	$241.50	$241.50
Purchase #6	$78.38	9.186%	$85.58	$85.58	$85.60	$85.60
Purchase #7	$169.60	12.511%	$190.8187	$190.82	$190.80	$190.80
7 purchase totals =	$937.06		$1,044.9530	$1,044.95	$1,044.95	$1,044.90