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	$166.93	3.504%	$172.7792	$172.78	$172.80	$172.80
Purchase #2	$46.81	13.248%	$53.0114	$53.01	$53.00	$53.00
Purchase #3	$36.60	6.120%	$38.8399	$38.84	$38.85	$38.80
Purchase #4	$56.46	13.144%	$63.8811	$63.88	$63.90	$63.90
Purchase #5	$192.51	9.184%	$210.1901	$210.19	$210.20	$210.20
Purchase #6	$30.45	6.813%	$32.5246	$32.52	$32.50	$32.50
Purchase #7	$163.83	6.347%	$174.2283	$174.23	$174.25	$174.20
7 purchase totals =	$693.59		$745.4546	$745.45	$745.50	$745.40