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	$100.86	12.572%	$113.5401	$113.54	$113.55	$113.50
Purchase #2	$51.83	7.860%	$55.9038	$55.90	$55.90	$55.90
Purchase #3	$59.54	7.795%	$64.1811	$64.18	$64.20	$64.20
Purchase #4	$162.31	4.381%	$169.4208	$169.42	$169.40	$169.40
Purchase #5	$143.33	7.188%	$153.6326	$153.63	$153.65	$153.60
Purchase #6	$69.38	4.735%	$72.6651	$72.67	$72.65	$72.70
Purchase #7	$161.88	9.406%	$177.1064	$177.11	$177.10	$177.10
7 purchase totals =	$749.13		$806.4499	$806.45	$806.45	$806.40