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	$164.59	4.759%	$172.4228	$172.42	$172.40	$172.40
Purchase #2	$128.96	9.723%	$141.4988	$141.50	$141.50	$141.50
Purchase #3	$69.48	11.249%	$77.2958	$77.30	$77.30	$77.30
Purchase #4	$63.32	7.333%	$67.9633	$67.96	$67.95	$68.00
Purchase #5	$31.65	12.222%	$35.5183	$35.52	$35.50	$35.50
Purchase #6	$208.58	5.283%	$219.5993	$219.60	$219.60	$219.60
Purchase #7	$112.73	9.115%	$123.0053	$123.01	$123.00	$123.00
7 purchase totals =	$779.31		$837.3036	$837.31	$837.25	$837.30