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	$71.82	8.579%	$77.9814	$77.98	$78.00	$78.00
Purchase #2	$239.40	6.637%	$255.289	$255.29	$255.30	$255.30
Purchase #3	$21.75	7.188%	$23.3134	$23.31	$23.30	$23.30
Purchase #4	$186.98	4.868%	$196.0822	$196.08	$196.10	$196.10
Purchase #5	$140.54	11.534%	$156.7499	$156.75	$156.75	$156.70
Purchase #6	$186.81	5.264%	$196.6437	$196.64	$196.65	$196.60
Purchase #7	$176.39	8.464%	$191.3196	$191.32	$191.30	$191.30
7 purchase totals =	$1,023.69		$1,097.3792	$1,097.37	$1,097.40	$1,097.30