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	$224.66	3.154%	$231.7458	$231.75	$231.75	$231.70
Purchase #2	$139.33	13.306%	$157.8692	$157.87	$157.85	$157.90
Purchase #3	$175.70	13.202%	$198.8959	$198.90	$198.90	$198.90
Purchase #4	$215.71	4.661%	$225.7642	$225.76	$225.75	$225.80
Purchase #5	$69.72	3.808%	$72.3749	$72.37	$72.35	$72.40
Purchase #6	$99.72	6.168%	$105.8707	$105.87	$105.85	$105.90
Purchase #7	$202.62	6.738%	$216.2725	$216.27	$216.25	$216.30
7 purchase totals =	$1,127.46		$1,208.7932	$1,208.79	$1,208.70	$1,208.90