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	$108.96	4.207%	$113.5439	$113.54	$113.55	$113.50
Purchase #2	$50.97	7.632%	$54.86	$54.86	$54.85	$54.90
Purchase #3	$203.81	3.304%	$210.5439	$210.54	$210.55	$210.50
Purchase #4	$70.36	11.595%	$78.5182	$78.52	$78.50	$78.50
Purchase #5	$51.36	5.290%	$54.0769	$54.08	$54.10	$54.10
Purchase #6	$173.33	4.293%	$180.7711	$180.77	$180.75	$180.80
Purchase #7	$128.84	7.380%	$138.3484	$138.35	$138.35	$138.30
7 purchase totals =	$787.63		$830.6624	$830.66	$830.65	$830.60