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	$112.64	9.604%	$123.4579	$123.46	$123.45	$123.50
Purchase #2	$53.77	4.847%	$56.3762	$56.38	$56.40	$56.40
Purchase #3	$35.60	11.140%	$39.5658	$39.57	$39.55	$39.60
Purchase #4	$159.77	7.407%	$171.6042	$171.60	$171.60	$171.60
Purchase #5	$245.53	11.329%	$273.3461	$273.35	$273.35	$273.30
Purchase #6	$168.97	6.115%	$179.3025	$179.30	$179.30	$179.30
Purchase #7	$111.93	13.256%	$126.7674	$126.77	$126.75	$126.80
7 purchase totals =	$888.21		$970.4201	$970.43	$970.40	$970.50