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	$89.52	13.347%	$101.4682	$101.47	$101.45	$101.50
Purchase #2	$72.85	10.484%	$80.4876	$80.49	$80.50	$80.50
Purchase #3	$59.72	9.187%	$65.2065	$65.21	$65.20	$65.20
Purchase #4	$250.66	9.728%	$275.0442	$275.04	$275.05	$275.00
Purchase #5	$180.38	11.334%	$200.8243	$200.82	$200.80	$200.80
Purchase #6	$160.75	3.333%	$166.1078	$166.11	$166.10	$166.10
Purchase #7	$205.38	6.131%	$217.9718	$217.97	$217.95	$218.00
7 purchase totals =	$1,019.26		$1,107.1104	$1,107.11	$1,107.05	$1,107.10