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	$205.29	13.161%	$232.3082	$232.31	$232.30	$232.30
Purchase #2	$158.54	6.248%	$168.4456	$168.45	$168.45	$168.40
Purchase #3	$47.25	4.612%	$49.4292	$49.43	$49.45	$49.40
Purchase #4	$176.45	11.550%	$196.83	$196.83	$196.85	$196.80
Purchase #5	$211.63	3.282%	$218.5757	$218.58	$218.60	$218.60
Purchase #6	$136.64	8.369%	$148.0754	$148.08	$148.10	$148.10
Purchase #7	$13.27	12.132%	$14.8799	$14.88	$14.90	$14.90
7 purchase totals =	$949.07		$1,028.5440	$1,028.56	$1,028.65	$1,028.50