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	$97.63	4.533%	$102.0556	$102.06	$102.05	$102.10
Purchase #2	$228.27	3.643%	$236.5859	$236.59	$236.60	$236.60
Purchase #3	$104.89	4.577%	$109.6908	$109.69	$109.70	$109.70
Purchase #4	$178.36	11.322%	$198.5539	$198.55	$198.55	$198.60
Purchase #5	$181.85	5.320%	$191.5244	$191.52	$191.50	$191.50
Purchase #6	$6.65	3.620%	$6.8907	$6.89	$6.90	$6.90
Purchase #7	$177.81	8.313%	$192.5913	$192.59	$192.60	$192.60
7 purchase totals =	$975.46		$1,037.8926	$1,037.89	$1,037.90	$1,038.00