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	$38.63	5.109%	$40.6036	$40.60	$40.60	$40.60
Purchase #2	$172.78	10.177%	$190.3638	$190.36	$190.35	$190.40
Purchase #3	$213.56	9.217%	$233.2438	$233.24	$233.25	$233.20
Purchase #4	$74.97	4.785%	$78.5573	$78.56	$78.55	$78.60
Purchase #5	$237.37	5.234%	$249.7939	$249.79	$249.80	$249.80
Purchase #6	$115.92	9.306%	$126.7075	$126.71	$126.70	$126.70
Purchase #7	$108.39	9.328%	$118.5006	$118.50	$118.50	$118.50
7 purchase totals =	$961.62		$1,037.7705	$1,037.76	$1,037.75	$1,037.80