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	$200.41	5.462%	$211.3564	$211.36	$211.35	$211.40
Purchase #2	$108.78	9.720%	$119.3534	$119.35	$119.35	$119.40
Purchase #3	$109.92	10.328%	$121.2725	$121.27	$121.25	$121.30
Purchase #4	$209.88	11.436%	$233.8819	$233.88	$233.90	$233.90
Purchase #5	$211.76	5.248%	$222.8732	$222.87	$222.85	$222.90
Purchase #6	$91.81	12.316%	$103.1173	$103.12	$103.10	$103.10
Purchase #7	$6.72	3.452%	$6.952	$6.95	$6.95	$7.00
7 purchase totals =	$939.28		$1,018.8067	$1,018.80	$1,018.75	$1,019.00