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	$32.57	6.454%	$34.6721	$34.67	$34.65	$34.70
Purchase #2	$164.45	13.615%	$186.8399	$186.84	$186.85	$186.80
Purchase #3	$72.75	5.331%	$76.6283	$76.63	$76.65	$76.60
Purchase #4	$186.67	5.443%	$196.8304	$196.83	$196.85	$196.80
Purchase #5	$230.54	5.216%	$242.565	$242.57	$242.55	$242.60
Purchase #6	$55.27	4.553%	$57.7864	$57.79	$57.80	$57.80
Purchase #7	$244.89	13.211%	$277.2424	$277.24	$277.25	$277.20
7 purchase totals =	$987.14		$1,072.5645	$1,072.57	$1,072.60	$1,072.50