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	$182.26	4.344%	$190.1774	$190.18	$190.20	$190.20
Purchase #2	$154.48	8.175%	$167.1087	$167.11	$167.10	$167.10
Purchase #3	$241.95	5.462%	$255.1653	$255.17	$255.15	$255.20
Purchase #4	$206.50	11.855%	$230.9806	$230.98	$231.00	$231.00
Purchase #5	$54.70	8.470%	$59.3331	$59.33	$59.35	$59.30
Purchase #6	$57.79	11.556%	$64.4682	$64.47	$64.45	$64.50
Purchase #7	$73.46	13.578%	$83.4344	$83.43	$83.45	$83.40
7 purchase totals =	$971.14		$1,050.6677	$1,050.67	$1,050.70	$1,050.70