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	$59.83	9.500%	$65.5139	$65.51	$65.50	$65.50
Purchase #2	$139.43	8.223%	$150.8953	$150.90	$150.90	$150.90
Purchase #3	$218.49	3.381%	$225.8771	$225.88	$225.90	$225.90
Purchase #4	$18.33	4.419%	$19.14	$19.14	$19.15	$19.10
Purchase #5	$28.44	13.366%	$32.2413	$32.24	$32.25	$32.20
Purchase #6	$147.95	8.748%	$160.8927	$160.89	$160.90	$160.90
Purchase #7	$57.64	6.398%	$61.3278	$61.33	$61.35	$61.30
7 purchase totals =	$670.11		$715.8881	$715.89	$715.95	$715.80