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	$197.72	4.578%	$206.7716	$206.77	$206.75	$206.80
Purchase #2	$68.30	6.248%	$72.5674	$72.57	$72.55	$72.60
Purchase #3	$140.50	5.312%	$147.9634	$147.96	$147.95	$148.00
Purchase #4	$62.29	3.630%	$64.5511	$64.55	$64.55	$64.60
Purchase #5	$111.59	10.703%	$123.5335	$123.53	$123.55	$123.50
Purchase #6	$243.53	11.849%	$272.3859	$272.39	$272.40	$272.40
Purchase #7	$209.94	9.718%	$230.342	$230.34	$230.35	$230.30
7 purchase totals =	$1,033.87		$1,118.1149	$1,118.11	$1,118.10	$1,118.20