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	$200.56	8.544%	$217.6958	$217.70	$217.70	$217.70
Purchase #2	$205.31	6.626%	$218.9138	$218.91	$218.90	$218.90
Purchase #3	$248.78	4.311%	$259.5049	$259.50	$259.50	$259.50
Purchase #4	$136.27	11.606%	$152.0855	$152.09	$152.10	$152.10
Purchase #5	$37.25	8.325%	$40.3511	$40.35	$40.35	$40.40
Purchase #6	$203.81	9.787%	$223.7569	$223.76	$223.75	$223.80
Purchase #7	$145.48	11.471%	$162.168	$162.17	$162.15	$162.20
7 purchase totals =	$1,177.46		$1,274.4760	$1,274.48	$1,274.45	$1,274.60