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	$62.84	7.518%	$67.5643	$67.56	$67.55	$67.60
Purchase #2	$163.28	13.682%	$185.62	$185.62	$185.60	$185.60
Purchase #3	$36.88	6.658%	$39.3355	$39.34	$39.35	$39.30
Purchase #4	$128.62	3.102%	$132.6098	$132.61	$132.60	$132.60
Purchase #5	$95.90	13.528%	$108.8734	$108.87	$108.85	$108.90
Purchase #6	$137.59	6.372%	$146.3572	$146.36	$146.35	$146.40
Purchase #7	$163.93	13.155%	$185.495	$185.50	$185.50	$185.50
7 purchase totals =	$789.04		$865.8552	$865.86	$865.80	$865.90