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	$133.32	12.438%	$149.9023	$149.90	$149.90	$149.90
Purchase #2	$33.88	11.254%	$37.6929	$37.69	$37.70	$37.70
Purchase #3	$53.54	7.632%	$57.6262	$57.63	$57.65	$57.60
Purchase #4	$173.96	13.440%	$197.3402	$197.34	$197.35	$197.30
Purchase #5	$70.67	11.633%	$78.891	$78.89	$78.90	$78.90
Purchase #6	$217.72	10.189%	$239.9035	$239.90	$239.90	$239.90
Purchase #7	$166.34	6.349%	$176.9009	$176.90	$176.90	$176.90
7 purchase totals =	$849.43		$938.2570	$938.25	$938.30	$938.20