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	$165.32	10.535%	$182.7365	$182.74	$182.75	$182.70
Purchase #2	$148.93	11.264%	$165.7055	$165.71	$165.70	$165.70
Purchase #3	$115.94	6.301%	$123.2454	$123.25	$123.25	$123.20
Purchase #4	$195.70	10.320%	$215.8962	$215.90	$215.90	$215.90
Purchase #5	$92.78	13.137%	$104.9685	$104.97	$104.95	$105.00
Purchase #6	$217.89	13.278%	$246.8214	$246.82	$246.80	$246.80
Purchase #7	$157.29	8.785%	$171.1079	$171.11	$171.10	$171.10
7 purchase totals =	$1,093.85		$1,210.4814	$1,210.50	$1,210.45	$1,210.40