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	$96.60	10.715%	$106.9507	$106.95	$106.95	$107.00
Purchase #2	$51.65	7.714%	$55.6343	$55.63	$55.65	$55.60
Purchase #3	$98.82	12.698%	$111.3682	$111.37	$111.35	$111.40
Purchase #4	$108.59	3.551%	$112.446	$112.45	$112.45	$112.40
Purchase #5	$15.61	5.126%	$16.4102	$16.41	$16.40	$16.40
Purchase #6	$70.56	3.635%	$73.1249	$73.12	$73.10	$73.10
Purchase #7	$112.78	6.271%	$119.8524	$119.85	$119.85	$119.90
7 purchase totals =	$554.61		$595.7867	$595.78	$595.75	$595.80