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	$105.96	10.373%	$116.9512	$116.95	$116.95	$117.00
Purchase #2	$40.35	4.594%	$42.2037	$42.20	$42.20	$42.20
Purchase #3	$63.52	5.820%	$67.2169	$67.22	$67.20	$67.20
Purchase #4	$43.93	10.448%	$48.5198	$48.52	$48.50	$48.50
Purchase #5	$53.71	5.620%	$56.7285	$56.73	$56.75	$56.70
Purchase #6	$152.90	12.255%	$171.6379	$171.64	$171.65	$171.60
Purchase #7	$172.76	6.783%	$184.4783	$184.48	$184.50	$184.50
7 purchase totals =	$633.13		$687.7363	$687.74	$687.75	$687.70