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	$208.55	5.298%	$219.599	$219.60	$219.60	$219.60
Purchase #2	$223.73	11.547%	$249.5641	$249.56	$249.55	$249.60
Purchase #3	$231.59	6.755%	$247.2339	$247.23	$247.25	$247.20
Purchase #4	$12.32	8.102%	$13.3182	$13.32	$13.30	$13.30
Purchase #5	$117.46	4.739%	$123.0264	$123.03	$123.05	$123.00
Purchase #6	$48.43	12.682%	$54.5719	$54.57	$54.55	$54.60
Purchase #7	$23.30	3.104%	$24.0232	$24.02	$24.00	$24.00
7 purchase totals =	$865.38		$931.3367	$931.33	$931.30	$931.30