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	$102.27	8.871%	$111.3424	$111.34	$111.35	$111.30
Purchase #2	$159.43	5.715%	$168.5414	$168.54	$168.55	$168.50
Purchase #3	$89.54	8.319%	$96.9888	$96.99	$97.00	$97.00
Purchase #4	$188.72	3.868%	$196.0197	$196.02	$196.00	$196.00
Purchase #5	$76.50	3.329%	$79.0467	$79.05	$79.05	$79.00
Purchase #6	$231.78	6.352%	$246.5027	$246.50	$246.50	$246.50
Purchase #7	$40.40	7.288%	$43.3444	$43.34	$43.35	$43.30
7 purchase totals =	$888.64		$941.7861	$941.78	$941.80	$941.60