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	$13.67	11.661%	$15.2641	$15.26	$15.25	$15.30
Purchase #2	$28.95	7.703%	$31.18	$31.18	$31.20	$31.20
Purchase #3	$109.58	5.730%	$115.8589	$115.86	$115.85	$115.90
Purchase #4	$212.96	4.167%	$221.834	$221.83	$221.85	$221.80
Purchase #5	$29.88	12.256%	$33.5421	$33.54	$33.55	$33.50
Purchase #6	$189.36	13.624%	$215.1584	$215.16	$215.15	$215.20
Purchase #7	$64.94	11.269%	$72.2581	$72.26	$72.25	$72.30
7 purchase totals =	$649.34		$705.0956	$705.09	$705.10	$705.20