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	$200.50	6.540%	$213.6127	$213.61	$213.60	$213.60
Purchase #2	$96.31	6.811%	$102.8697	$102.87	$102.85	$102.90
Purchase #3	$10.71	11.280%	$11.9181	$11.92	$11.90	$11.90
Purchase #4	$147.67	12.518%	$166.1553	$166.16	$166.15	$166.20
Purchase #5	$131.45	11.156%	$146.1146	$146.11	$146.10	$146.10
Purchase #6	$186.38	11.827%	$208.4232	$208.42	$208.40	$208.40
Purchase #7	$73.42	7.374%	$78.834	$78.83	$78.85	$78.80
7 purchase totals =	$846.44		$927.9276	$927.92	$927.85	$927.90