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	$86.81	4.465%	$90.6861	$90.69	$90.70	$90.70
Purchase #2	$72.86	11.673%	$81.3649	$81.36	$81.35	$81.40
Purchase #3	$220.83	11.806%	$246.9012	$246.90	$246.90	$246.90
Purchase #4	$202.25	10.696%	$223.8827	$223.88	$223.90	$223.90
Purchase #5	$101.33	6.564%	$107.9813	$107.98	$108.00	$108.00
Purchase #6	$126.92	3.578%	$131.4612	$131.46	$131.45	$131.50
Purchase #7	$236.34	5.274%	$248.8046	$248.80	$248.80	$248.80
7 purchase totals =	$1,047.34		$1,131.0820	$1,131.07	$1,131.10	$1,131.20