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	$197.55	6.507%	$210.4046	$210.40	$210.40	$210.40
Purchase #2	$89.34	3.549%	$92.5107	$92.51	$92.50	$92.50
Purchase #3	$208.88	3.439%	$216.0634	$216.06	$216.05	$216.10
Purchase #4	$137.37	4.205%	$143.1464	$143.15	$143.15	$143.10
Purchase #5	$74.30	10.214%	$81.889	$81.89	$81.90	$81.90
Purchase #6	$56.37	13.260%	$63.8447	$63.84	$63.85	$63.80
Purchase #7	$183.51	7.169%	$196.6658	$196.67	$196.65	$196.70
7 purchase totals =	$947.32		$1,004.5246	$1,004.52	$1,004.50	$1,004.50