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	$70.26	4.523%	$73.4379	$73.44	$73.45	$73.40
Purchase #2	$152.67	9.634%	$167.3782	$167.38	$167.40	$167.40
Purchase #3	$183.98	13.858%	$209.4759	$209.48	$209.50	$209.50
Purchase #4	$66.75	10.643%	$73.8542	$73.85	$73.85	$73.90
Purchase #5	$175.51	4.216%	$182.9095	$182.91	$182.90	$182.90
Purchase #6	$108.31	10.122%	$119.2731	$119.27	$119.25	$119.30
Purchase #7	$245.66	3.856%	$255.1326	$255.13	$255.15	$255.10
7 purchase totals =	$1,003.14		$1,081.4614	$1,081.46	$1,081.50	$1,081.50