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	$132.41	7.846%	$142.7989	$142.80	$142.80	$142.80
Purchase #2	$169.97	6.590%	$181.171	$181.17	$181.15	$181.20
Purchase #3	$112.36	3.330%	$116.1016	$116.10	$116.10	$116.10
Purchase #4	$129.69	7.183%	$139.0056	$139.01	$139.00	$139.00
Purchase #5	$50.37	3.417%	$52.0911	$52.09	$52.10	$52.10
Purchase #6	$142.52	8.639%	$154.8323	$154.83	$154.85	$154.80
Purchase #7	$152.84	11.158%	$169.8939	$169.89	$169.90	$169.90
7 purchase totals =	$890.16		$955.8944	$955.89	$955.90	$955.90