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	$136.37	3.789%	$141.5371	$141.54	$141.55	$141.50
Purchase #2	$153.66	5.306%	$161.8132	$161.81	$161.80	$161.80
Purchase #3	$82.81	10.530%	$91.5299	$91.53	$91.55	$91.50
Purchase #4	$46.65	6.207%	$49.5456	$49.55	$49.55	$49.50
Purchase #5	$234.90	11.254%	$261.3356	$261.34	$261.35	$261.30
Purchase #6	$86.59	5.682%	$91.51	$91.51	$91.50	$91.50
Purchase #7	$226.40	5.242%	$238.2679	$238.27	$238.25	$238.30
7 purchase totals =	$967.38		$1,035.5393	$1,035.55	$1,035.55	$1,035.40