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	$163.71	4.836%	$171.627	$171.63	$171.65	$171.60
Purchase #2	$179.26	9.683%	$196.6177	$196.62	$196.60	$196.60
Purchase #3	$170.40	12.585%	$191.8448	$191.84	$191.85	$191.80
Purchase #4	$191.70	13.204%	$217.0121	$217.01	$217.00	$217.00
Purchase #5	$243.25	4.557%	$254.3349	$254.33	$254.35	$254.30
Purchase #6	$242.92	10.690%	$268.8881	$268.89	$268.90	$268.90
Purchase #7	$166.52	7.871%	$179.6268	$179.63	$179.65	$179.60
7 purchase totals =	$1,357.76		$1,479.9514	$1,479.95	$1,480.00	$1,479.80