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	$206.88	8.230%	$223.9062	$223.91	$223.90	$223.90
Purchase #2	$84.43	13.217%	$95.5891	$95.59	$95.60	$95.60
Purchase #3	$154.81	5.837%	$163.8463	$163.85	$163.85	$163.80
Purchase #4	$244.78	9.722%	$268.5775	$268.58	$268.60	$268.60
Purchase #5	$56.46	5.812%	$59.7415	$59.74	$59.75	$59.70
Purchase #6	$153.96	13.626%	$174.9386	$174.94	$174.95	$174.90
Purchase #7	$151.27	10.715%	$167.4786	$167.48	$167.50	$167.50
7 purchase totals =	$1,052.59		$1,154.0778	$1,154.09	$1,154.15	$1,154.00