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	$61.61	7.207%	$66.0502	$66.05	$66.05	$66.10
Purchase #2	$249.83	6.289%	$265.5418	$265.54	$265.55	$265.50
Purchase #3	$206.63	9.868%	$227.0202	$227.02	$227.00	$227.00
Purchase #4	$77.67	10.594%	$85.8984	$85.90	$85.90	$85.90
Purchase #5	$64.84	9.716%	$71.1399	$71.14	$71.15	$71.10
Purchase #6	$217.40	10.650%	$240.5531	$240.55	$240.55	$240.60
Purchase #7	$96.59	6.472%	$102.8413	$102.84	$102.85	$102.80
7 purchase totals =	$974.57		$1,059.0449	$1,059.04	$1,059.05	$1,059.00