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	$233.58	12.761%	$263.3871	$263.39	$263.40	$263.40
Purchase #2	$223.73	4.790%	$234.4467	$234.45	$234.45	$234.40
Purchase #3	$167.53	13.754%	$190.5721	$190.57	$190.55	$190.60
Purchase #4	$26.71	9.670%	$29.2929	$29.29	$29.30	$29.30
Purchase #5	$155.83	13.795%	$177.3267	$177.33	$177.35	$177.30
Purchase #6	$7.90	12.695%	$8.9029	$8.90	$8.90	$8.90
Purchase #7	$142.85	9.759%	$156.7907	$156.79	$156.80	$156.80
7 purchase totals =	$958.13		$1,060.7191	$1,060.72	$1,060.75	$1,060.70