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	$42.75	9.122%	$46.6497	$46.65	$46.65	$46.60
Purchase #2	$74.86	6.612%	$79.8097	$79.81	$79.80	$79.80
Purchase #3	$63.61	13.641%	$72.287	$72.29	$72.30	$72.30
Purchase #4	$215.29	5.648%	$227.4496	$227.45	$227.45	$227.40
Purchase #5	$41.86	11.348%	$46.6103	$46.61	$46.60	$46.60
Purchase #6	$213.69	4.475%	$223.2526	$223.25	$223.25	$223.30
Purchase #7	$84.55	11.382%	$94.1735	$94.17	$94.15	$94.20
7 purchase totals =	$736.61		$790.2324	$790.23	$790.20	$790.20