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	$204.70	3.730%	$212.3353	$212.34	$212.35	$212.30
Purchase #2	$223.26	13.385%	$253.1434	$253.14	$253.15	$253.10
Purchase #3	$234.84	6.818%	$250.8514	$250.85	$250.85	$250.90
Purchase #4	$196.96	3.874%	$204.5902	$204.59	$204.60	$204.60
Purchase #5	$65.35	8.329%	$70.793	$70.79	$70.80	$70.80
Purchase #6	$132.98	3.464%	$137.5864	$137.59	$137.60	$137.60
Purchase #7	$40.59	7.206%	$43.5149	$43.51	$43.50	$43.50
7 purchase totals =	$1,098.68		$1,172.8146	$1,172.81	$1,172.85	$1,172.80