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	$200.95	12.445%	$225.9582	$225.96	$225.95	$226.00
Purchase #2	$54.64	5.820%	$57.82	$57.82	$57.80	$57.80
Purchase #3	$141.75	13.165%	$160.4114	$160.41	$160.40	$160.40
Purchase #4	$23.50	7.312%	$25.2183	$25.22	$25.20	$25.20
Purchase #5	$72.66	13.696%	$82.6115	$82.61	$82.60	$82.60
Purchase #6	$207.45	10.110%	$228.4232	$228.42	$228.40	$228.40
Purchase #7	$241.27	3.448%	$249.589	$249.59	$249.60	$249.60
7 purchase totals =	$942.22		$1,030.0316	$1,030.03	$1,029.95	$1,030.00