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	$186.66	4.140%	$194.3877	$194.39	$194.40	$194.40
Purchase #2	$86.76	4.629%	$90.7761	$90.78	$90.80	$90.80
Purchase #3	$230.50	9.114%	$251.5078	$251.51	$251.50	$251.50
Purchase #4	$215.78	3.261%	$222.8166	$222.82	$222.80	$222.80
Purchase #5	$213.55	6.809%	$228.0906	$228.09	$228.10	$228.10
Purchase #6	$64.36	4.865%	$67.4911	$67.49	$67.50	$67.50
Purchase #7	$246.97	10.335%	$272.4943	$272.49	$272.50	$272.50
7 purchase totals =	$1,244.58		$1,327.5642	$1,327.57	$1,327.60	$1,327.60