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	$190.70	9.375%	$208.5781	$208.58	$208.60	$208.60
Purchase #2	$233.71	7.495%	$251.2266	$251.23	$251.25	$251.20
Purchase #3	$103.98	7.537%	$111.817	$111.82	$111.80	$111.80
Purchase #4	$24.95	3.771%	$25.8909	$25.89	$25.90	$25.90
Purchase #5	$196.48	13.684%	$223.3663	$223.37	$223.35	$223.40
Purchase #6	$161.62	4.113%	$168.2674	$168.27	$168.25	$168.30
Purchase #7	$78.78	7.112%	$84.3828	$84.38	$84.40	$84.40
7 purchase totals =	$990.22		$1,073.5291	$1,073.54	$1,073.55	$1,073.60