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	$222.77	11.542%	$248.4821	$248.48	$248.50	$248.50
Purchase #2	$232.57	11.108%	$258.4039	$258.40	$258.40	$258.40
Purchase #3	$131.37	7.581%	$141.3292	$141.33	$141.35	$141.30
Purchase #4	$10.87	6.617%	$11.5893	$11.59	$11.60	$11.60
Purchase #5	$101.68	9.558%	$111.3986	$111.40	$111.40	$111.40
Purchase #6	$112.98	11.534%	$126.0111	$126.01	$126.00	$126.00
Purchase #7	$247.33	8.400%	$268.1057	$268.11	$268.10	$268.10
7 purchase totals =	$1,059.57		$1,165.3199	$1,165.32	$1,165.35	$1,165.30