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	$121.28	4.268%	$126.4562	$126.46	$126.45	$126.50
Purchase #2	$120.93	12.869%	$136.4925	$136.49	$136.50	$136.50
Purchase #3	$246.48	5.459%	$259.9353	$259.94	$259.95	$259.90
Purchase #4	$66.40	10.656%	$73.4756	$73.48	$73.50	$73.50
Purchase #5	$188.89	5.514%	$199.3054	$199.31	$199.30	$199.30
Purchase #6	$173.38	6.156%	$184.0533	$184.05	$184.05	$184.10
Purchase #7	$116.38	3.499%	$120.4521	$120.45	$120.45	$120.50
7 purchase totals =	$1,033.74		$1,100.1704	$1,100.18	$1,100.20	$1,100.30