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	$59.38	5.469%	$62.6275	$62.63	$62.65	$62.60
Purchase #2	$91.86	4.293%	$95.8035	$95.80	$95.80	$95.80
Purchase #3	$79.65	13.524%	$90.4219	$90.42	$90.40	$90.40
Purchase #4	$5.96	12.235%	$6.6892	$6.69	$6.70	$6.70
Purchase #5	$161.39	9.248%	$176.3153	$176.32	$176.30	$176.30
Purchase #6	$111.46	10.505%	$123.1689	$123.17	$123.15	$123.20
Purchase #7	$106.40	12.143%	$119.3202	$119.32	$119.30	$119.30
7 purchase totals =	$616.10		$674.3465	$674.35	$674.30	$674.30