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	$82.61	4.164%	$86.0499	$86.05	$86.05	$86.00
Purchase #2	$162.89	10.826%	$180.5245	$180.52	$180.50	$180.50
Purchase #3	$96.54	9.233%	$105.4535	$105.45	$105.45	$105.50
Purchase #4	$27.95	12.219%	$31.3652	$31.37	$31.35	$31.40
Purchase #5	$215.61	3.344%	$222.82	$222.82	$222.80	$222.80
Purchase #6	$156.29	6.826%	$166.9584	$166.96	$166.95	$167.00
Purchase #7	$223.88	11.125%	$248.7867	$248.79	$248.80	$248.80
7 purchase totals =	$965.77		$1,041.9582	$1,041.96	$1,041.90	$1,042.00