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	$131.87	8.689%	$143.3282	$143.33	$143.35	$143.30
Purchase #2	$114.34	10.440%	$126.2771	$126.28	$126.30	$126.30
Purchase #3	$217.56	6.317%	$231.3033	$231.30	$231.30	$231.30
Purchase #4	$51.46	9.741%	$56.4727	$56.47	$56.45	$56.50
Purchase #5	$5.95	6.372%	$6.3291	$6.33	$6.35	$6.30
Purchase #6	$113.59	8.544%	$123.2951	$123.30	$123.30	$123.30
Purchase #7	$68.97	3.637%	$71.4784	$71.48	$71.50	$71.50
7 purchase totals =	$703.74		$758.4839	$758.49	$758.55	$758.50