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	$202.83	9.760%	$222.6262	$222.63	$222.65	$222.60
Purchase #2	$237.83	13.456%	$269.8324	$269.83	$269.85	$269.80
Purchase #3	$6.97	13.705%	$7.9252	$7.93	$7.95	$7.90
Purchase #4	$104.35	7.824%	$112.5143	$112.51	$112.50	$112.50
Purchase #5	$246.27	11.672%	$275.0146	$275.01	$275.00	$275.00
Purchase #6	$27.87	9.495%	$30.5163	$30.52	$30.50	$30.50
Purchase #7	$80.50	7.531%	$86.5625	$86.56	$86.55	$86.60
7 purchase totals =	$906.62		$1,004.9915	$1,004.99	$1,005.00	$1,004.90