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	$131.83	3.231%	$136.0894	$136.09	$136.10	$136.10
Purchase #2	$49.91	4.114%	$51.9633	$51.96	$51.95	$52.00
Purchase #3	$229.31	13.768%	$260.8814	$260.88	$260.90	$260.90
Purchase #4	$239.86	3.717%	$248.7756	$248.78	$248.80	$248.80
Purchase #5	$26.37	10.196%	$29.0587	$29.06	$29.05	$29.10
Purchase #6	$112.33	6.217%	$119.3136	$119.31	$119.30	$119.30
Purchase #7	$176.54	11.510%	$196.8598	$196.86	$196.85	$196.90
7 purchase totals =	$966.15		$1,042.9418	$1,042.94	$1,042.95	$1,043.10