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	$54.56	9.791%	$59.902	$59.90	$59.90	$59.90
Purchase #2	$67.36	12.371%	$75.6931	$75.69	$75.70	$75.70
Purchase #3	$181.35	9.509%	$198.5946	$198.59	$198.60	$198.60
Purchase #4	$144.61	4.734%	$151.4558	$151.46	$151.45	$151.50
Purchase #5	$90.25	12.219%	$101.2776	$101.28	$101.30	$101.30
Purchase #6	$234.65	6.603%	$250.1439	$250.14	$250.15	$250.10
Purchase #7	$109.63	13.675%	$124.6219	$124.62	$124.60	$124.60
7 purchase totals =	$882.41		$961.6889	$961.68	$961.70	$961.70