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	$62.47	3.584%	$64.7089	$64.71	$64.70	$64.70
Purchase #2	$49.85	3.404%	$51.5469	$51.55	$51.55	$51.50
Purchase #3	$150.41	6.487%	$160.1671	$160.17	$160.15	$160.20
Purchase #4	$113.78	3.488%	$117.7486	$117.75	$117.75	$117.70
Purchase #5	$185.38	7.595%	$199.4596	$199.46	$199.45	$199.50
Purchase #6	$52.86	5.808%	$55.9301	$55.93	$55.95	$55.90
Purchase #7	$18.67	6.330%	$19.8518	$19.85	$19.85	$19.90
7 purchase totals =	$633.42		$669.4130	$669.42	$669.40	$669.40