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	$226.88	9.741%	$248.9804	$248.98	$249.00	$249.00
Purchase #2	$161.91	8.153%	$175.1105	$175.11	$175.10	$175.10
Purchase #3	$95.75	5.254%	$100.7807	$100.78	$100.80	$100.80
Purchase #4	$96.91	5.663%	$102.398	$102.40	$102.40	$102.40
Purchase #5	$102.34	9.401%	$111.961	$111.96	$111.95	$112.00
Purchase #6	$196.63	4.347%	$205.1775	$205.18	$205.20	$205.20
Purchase #7	$75.95	3.350%	$78.4943	$78.49	$78.50	$78.50
7 purchase totals =	$956.37		$1,022.9024	$1,022.90	$1,022.95	$1,023.00