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	$57.86	13.830%	$65.862	$65.86	$65.85	$65.90
Purchase #2	$177.84	10.265%	$196.0953	$196.10	$196.10	$196.10
Purchase #3	$82.39	11.223%	$91.6366	$91.64	$91.65	$91.60
Purchase #4	$152.54	5.504%	$160.9358	$160.94	$160.95	$160.90
Purchase #5	$235.34	12.829%	$265.5318	$265.53	$265.55	$265.50
Purchase #6	$78.33	5.395%	$82.5559	$82.56	$82.55	$82.60
Purchase #7	$198.98	7.265%	$213.4359	$213.44	$213.45	$213.40
7 purchase totals =	$983.28		$1,076.0533	$1,076.07	$1,076.10	$1,076.00