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	$131.37	8.632%	$142.7099	$142.71	$142.70	$142.70
Purchase #2	$83.37	7.144%	$89.326	$89.33	$89.35	$89.30
Purchase #3	$112.69	12.118%	$126.3458	$126.35	$126.35	$126.30
Purchase #4	$50.54	7.345%	$54.2522	$54.25	$54.25	$54.30
Purchase #5	$217.81	5.359%	$229.4824	$229.48	$229.50	$229.50
Purchase #6	$104.71	3.858%	$108.7497	$108.75	$108.75	$108.70
Purchase #7	$70.93	7.442%	$76.2086	$76.21	$76.20	$76.20
7 purchase totals =	$771.42		$827.0746	$827.08	$827.10	$827.00