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	$221.27	10.196%	$243.8307	$243.83	$243.85	$243.80
Purchase #2	$72.29	12.693%	$81.4658	$81.47	$81.45	$81.50
Purchase #3	$40.56	5.146%	$42.6472	$42.65	$42.65	$42.60
Purchase #4	$112.58	4.567%	$117.7215	$117.72	$117.70	$117.70
Purchase #5	$18.73	10.789%	$20.7508	$20.75	$20.75	$20.80
Purchase #6	$107.95	3.578%	$111.8125	$111.81	$111.80	$111.80
Purchase #7	$105.44	12.865%	$119.0049	$119.00	$119.00	$119.00
7 purchase totals =	$678.82		$737.2334	$737.23	$737.20	$737.20