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	$129.80	11.826%	$145.1501	$145.15	$145.15	$145.20
Purchase #2	$107.75	11.764%	$120.4257	$120.43	$120.45	$120.40
Purchase #3	$43.49	5.441%	$45.8563	$45.86	$45.85	$45.90
Purchase #4	$222.66	11.764%	$248.8537	$248.85	$248.85	$248.90
Purchase #5	$177.94	10.469%	$196.5685	$196.57	$196.55	$196.60
Purchase #6	$233.91	3.747%	$242.6746	$242.67	$242.65	$242.70
Purchase #7	$152.40	11.490%	$169.9108	$169.91	$169.90	$169.90
7 purchase totals =	$1,067.95		$1,169.4397	$1,169.44	$1,169.40	$1,169.60