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	$169.90	6.159%	$180.3641	$180.36	$180.35	$180.40
Purchase #2	$114.32	7.818%	$123.2575	$123.26	$123.25	$123.30
Purchase #3	$125.71	3.517%	$130.1312	$130.13	$130.15	$130.10
Purchase #4	$126.43	4.325%	$131.8981	$131.90	$131.90	$131.90
Purchase #5	$109.81	12.779%	$123.8426	$123.84	$123.85	$123.80
Purchase #6	$169.81	9.833%	$186.5074	$186.51	$186.50	$186.50
Purchase #7	$231.80	11.146%	$257.6364	$257.64	$257.65	$257.60
7 purchase totals =	$1,047.78		$1,133.6373	$1,133.64	$1,133.65	$1,133.60