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	$114.52	8.173%	$123.8797	$123.88	$123.90	$123.90
Purchase #2	$235.53	9.264%	$257.3495	$257.35	$257.35	$257.30
Purchase #3	$48.82	13.331%	$55.3282	$55.33	$55.35	$55.30
Purchase #4	$126.38	4.718%	$132.3426	$132.34	$132.35	$132.30
Purchase #5	$146.93	10.658%	$162.5898	$162.59	$162.60	$162.60
Purchase #6	$223.90	4.270%	$233.4605	$233.46	$233.45	$233.50
Purchase #7	$88.79	12.796%	$100.1516	$100.15	$100.15	$100.20
7 purchase totals =	$984.87		$1,065.1019	$1,065.10	$1,065.15	$1,065.10