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	$135.33	7.152%	$145.0088	$145.01	$145.00	$145.00
Purchase #2	$78.83	12.319%	$88.5411	$88.54	$88.55	$88.50
Purchase #3	$43.41	4.731%	$45.4637	$45.46	$45.45	$45.50
Purchase #4	$237.66	4.524%	$248.4117	$248.41	$248.40	$248.40
Purchase #5	$121.33	9.406%	$132.7423	$132.74	$132.75	$132.70
Purchase #6	$113.44	6.608%	$120.9361	$120.94	$120.95	$120.90
Purchase #7	$215.86	9.549%	$236.4725	$236.47	$236.45	$236.50
7 purchase totals =	$945.86		$1,017.5762	$1,017.57	$1,017.55	$1,017.50