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	$64.44	13.281%	$72.9983	$73.00	$73.00	$73.00
Purchase #2	$156.83	5.118%	$164.8566	$164.86	$164.85	$164.90
Purchase #3	$52.63	13.193%	$59.5735	$59.57	$59.55	$59.60
Purchase #4	$226.73	12.446%	$254.9488	$254.95	$254.95	$254.90
Purchase #5	$179.35	4.127%	$186.7518	$186.75	$186.75	$186.80
Purchase #6	$95.57	4.180%	$99.5648	$99.56	$99.55	$99.60
Purchase #7	$97.44	5.546%	$102.844	$102.84	$102.85	$102.80
7 purchase totals =	$872.99		$941.5378	$941.53	$941.50	$941.60