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	$210.26	8.279%	$227.6674	$227.67	$227.65	$227.70
Purchase #2	$210.87	10.455%	$232.9165	$232.92	$232.90	$232.90
Purchase #3	$116.83	9.664%	$128.1205	$128.12	$128.10	$128.10
Purchase #4	$34.26	4.866%	$35.9271	$35.93	$35.95	$35.90
Purchase #5	$160.29	12.114%	$179.7075	$179.71	$179.70	$179.70
Purchase #6	$82.86	8.664%	$90.039	$90.04	$90.05	$90.00
Purchase #7	$73.69	6.593%	$78.5484	$78.55	$78.55	$78.50
7 purchase totals =	$889.06		$972.9264	$972.94	$972.90	$972.80