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	$53.80	10.396%	$59.393	$59.39	$59.40	$59.40
Purchase #2	$189.88	13.480%	$215.4758	$215.48	$215.50	$215.50
Purchase #3	$217.61	9.459%	$238.1937	$238.19	$238.20	$238.20
Purchase #4	$174.33	3.556%	$180.5292	$180.53	$180.55	$180.50
Purchase #5	$161.41	3.424%	$166.9367	$166.94	$166.95	$166.90
Purchase #6	$95.84	12.545%	$107.8631	$107.86	$107.85	$107.90
Purchase #7	$10.37	4.552%	$10.842	$10.84	$10.85	$10.80
7 purchase totals =	$903.24		$979.2335	$979.23	$979.30	$979.20