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	$154.39	13.109%	$174.629	$174.63	$174.65	$174.60
Purchase #2	$98.79	13.236%	$111.8658	$111.87	$111.85	$111.90
Purchase #3	$157.47	6.586%	$167.841	$167.84	$167.85	$167.80
Purchase #4	$125.33	13.133%	$141.7896	$141.79	$141.80	$141.80
Purchase #5	$242.30	9.527%	$265.3839	$265.38	$265.40	$265.40
Purchase #6	$94.67	4.387%	$98.8232	$98.82	$98.80	$98.80
Purchase #7	$177.76	6.169%	$188.726	$188.73	$188.75	$188.70
7 purchase totals =	$1,050.71		$1,149.0585	$1,149.06	$1,149.10	$1,149.00