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	$222.52	13.846%	$253.3301	$253.33	$253.35	$253.30
Purchase #2	$171.83	7.439%	$184.6124	$184.61	$184.60	$184.60
Purchase #3	$40.57	7.647%	$43.6724	$43.67	$43.65	$43.70
Purchase #4	$159.45	12.595%	$179.5327	$179.53	$179.55	$179.50
Purchase #5	$103.57	13.128%	$117.1667	$117.17	$117.15	$117.20
Purchase #6	$29.46	6.589%	$31.4011	$31.40	$31.40	$31.40
Purchase #7	$250.28	12.293%	$281.0469	$281.05	$281.05	$281.00
7 purchase totals =	$977.68		$1,090.7623	$1,090.76	$1,090.75	$1,090.70