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	$33.84	13.610%	$38.4456	$38.45	$38.45	$38.40
Purchase #2	$137.65	9.248%	$150.3799	$150.38	$150.40	$150.40
Purchase #3	$181.58	6.213%	$192.8616	$192.86	$192.85	$192.90
Purchase #4	$128.29	11.392%	$142.9048	$142.90	$142.90	$142.90
Purchase #5	$61.63	3.601%	$63.8493	$63.85	$63.85	$63.80
Purchase #6	$166.26	8.465%	$180.3339	$180.33	$180.35	$180.30
Purchase #7	$89.40	12.871%	$100.9067	$100.91	$100.90	$100.90
7 purchase totals =	$798.65		$869.6818	$869.68	$869.70	$869.60