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	$94.98	9.190%	$103.7087	$103.71	$103.70	$103.70
Purchase #2	$15.75	11.109%	$17.4997	$17.50	$17.50	$17.50
Purchase #3	$218.72	11.449%	$243.7613	$243.76	$243.75	$243.80
Purchase #4	$25.71	12.484%	$28.9196	$28.92	$28.90	$28.90
Purchase #5	$199.41	11.689%	$222.719	$222.72	$222.70	$222.70
Purchase #6	$118.92	10.539%	$131.453	$131.45	$131.45	$131.50
Purchase #7	$201.57	5.856%	$213.3739	$213.37	$213.35	$213.40
7 purchase totals =	$875.06		$961.4352	$961.43	$961.35	$961.50