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	$92.25	3.465%	$95.4465	$95.45	$95.45	$95.40
Purchase #2	$164.59	9.711%	$180.5733	$180.57	$180.55	$180.60
Purchase #3	$92.96	13.397%	$105.4139	$105.41	$105.40	$105.40
Purchase #4	$68.33	13.580%	$77.6092	$77.61	$77.60	$77.60
Purchase #5	$118.62	8.520%	$128.7264	$128.73	$128.75	$128.70
Purchase #6	$190.80	13.561%	$216.6744	$216.67	$216.65	$216.70
Purchase #7	$208.73	12.167%	$234.1262	$234.13	$234.15	$234.10
7 purchase totals =	$936.28		$1,038.5699	$1,038.57	$1,038.55	$1,038.50