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	$100.27	9.500%	$109.7957	$109.80	$109.80	$109.80
Purchase #2	$218.49	6.735%	$233.2053	$233.21	$233.20	$233.20
Purchase #3	$177.33	10.705%	$196.3132	$196.31	$196.30	$196.30
Purchase #4	$196.30	11.509%	$218.8922	$218.89	$218.90	$218.90
Purchase #5	$179.71	7.715%	$193.5746	$193.57	$193.55	$193.60
Purchase #6	$22.84	5.752%	$24.1538	$24.15	$24.15	$24.20
Purchase #7	$26.83	9.541%	$29.3899	$29.39	$29.40	$29.40
7 purchase totals =	$921.77		$1,005.3247	$1,005.32	$1,005.30	$1,005.40