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	$177.37	11.572%	$197.8953	$197.90	$197.90	$197.90
Purchase #2	$213.82	13.783%	$243.2908	$243.29	$243.30	$243.30
Purchase #3	$182.85	3.650%	$189.524	$189.52	$189.50	$189.50
Purchase #4	$210.37	6.413%	$223.861	$223.86	$223.85	$223.90
Purchase #5	$134.81	5.656%	$142.4349	$142.43	$142.45	$142.40
Purchase #6	$88.70	7.191%	$95.0784	$95.08	$95.10	$95.10
Purchase #7	$54.40	4.348%	$56.7653	$56.77	$56.75	$56.80
7 purchase totals =	$1,062.32		$1,148.8497	$1,148.85	$1,148.85	$1,148.90