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	$82.82	8.229%	$89.6353	$89.64	$89.65	$89.60
Purchase #2	$95.88	8.427%	$103.9598	$103.96	$103.95	$104.00
Purchase #3	$153.94	9.188%	$168.084	$168.08	$168.10	$168.10
Purchase #4	$225.46	4.702%	$236.0611	$236.06	$236.05	$236.10
Purchase #5	$144.94	4.404%	$151.3232	$151.32	$151.30	$151.30
Purchase #6	$232.85	6.458%	$247.8875	$247.89	$247.90	$247.90
Purchase #7	$184.70	4.462%	$192.9413	$192.94	$192.95	$192.90
7 purchase totals =	$1,120.59		$1,189.8922	$1,189.89	$1,189.90	$1,189.90