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	$168.70	4.767%	$176.7419	$176.74	$176.75	$176.70
Purchase #2	$151.38	9.328%	$165.5007	$165.50	$165.50	$165.50
Purchase #3	$40.57	12.376%	$45.5909	$45.59	$45.60	$45.60
Purchase #4	$125.73	10.711%	$139.1969	$139.20	$139.20	$139.20
Purchase #5	$166.36	13.801%	$189.3193	$189.32	$189.30	$189.30
Purchase #6	$80.37	7.660%	$86.5263	$86.53	$86.55	$86.50
Purchase #7	$43.47	12.625%	$48.9581	$48.96	$48.95	$49.00
7 purchase totals =	$776.58		$851.8341	$851.84	$851.85	$851.80