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	$80.80	8.297%	$87.504	$87.50	$87.50	$87.50
Purchase #2	$163.94	13.394%	$185.8981	$185.90	$185.90	$185.90
Purchase #3	$196.68	4.432%	$205.3969	$205.40	$205.40	$205.40
Purchase #4	$176.51	3.632%	$182.9208	$182.92	$182.90	$182.90
Purchase #5	$150.81	13.566%	$171.2689	$171.27	$171.25	$171.30
Purchase #6	$122.83	7.196%	$131.6688	$131.67	$131.65	$131.70
Purchase #7	$135.38	8.556%	$146.9631	$146.96	$146.95	$147.00
7 purchase totals =	$1,026.95		$1,111.6206	$1,111.62	$1,111.55	$1,111.70