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	$220.48	5.162%	$231.8612	$231.86	$231.85	$231.90
Purchase #2	$55.69	7.231%	$59.7169	$59.72	$59.70	$59.70
Purchase #3	$187.52	13.831%	$213.4559	$213.46	$213.45	$213.50
Purchase #4	$171.27	8.655%	$186.0934	$186.09	$186.10	$186.10
Purchase #5	$144.34	13.156%	$163.3294	$163.33	$163.35	$163.30
Purchase #6	$231.94	9.705%	$254.4498	$254.45	$254.45	$254.40
Purchase #7	$67.98	5.721%	$71.8691	$71.87	$71.85	$71.90
7 purchase totals =	$1,079.22		$1,180.7757	$1,180.78	$1,180.75	$1,180.80