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	$84.75	13.690%	$96.3523	$96.35	$96.35	$96.40
Purchase #2	$106.84	13.158%	$120.898	$120.90	$120.90	$120.90
Purchase #3	$133.59	6.220%	$141.8993	$141.90	$141.90	$141.90
Purchase #4	$63.38	10.153%	$69.815	$69.82	$69.80	$69.80
Purchase #5	$149.50	9.800%	$164.151	$164.15	$164.15	$164.20
Purchase #6	$197.31	12.816%	$222.5972	$222.60	$222.60	$222.60
Purchase #7	$125.46	4.755%	$131.4256	$131.43	$131.45	$131.40
7 purchase totals =	$860.83		$947.1384	$947.15	$947.15	$947.20