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	$119.63	11.862%	$133.8205	$133.82	$133.80	$133.80
Purchase #2	$104.96	6.119%	$111.3825	$111.38	$111.40	$111.40
Purchase #3	$221.74	9.550%	$242.9162	$242.92	$242.90	$242.90
Purchase #4	$43.63	9.809%	$47.9097	$47.91	$47.90	$47.90
Purchase #5	$181.45	7.387%	$194.8537	$194.85	$194.85	$194.90
Purchase #6	$63.67	4.636%	$66.6217	$66.62	$66.60	$66.60
Purchase #7	$240.41	6.215%	$255.3515	$255.35	$255.35	$255.40
7 purchase totals =	$975.49		$1,052.8558	$1,052.85	$1,052.80	$1,052.90