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	$51.90	7.872%	$55.9856	$55.99	$56.00	$56.00
Purchase #2	$174.70	12.555%	$196.6336	$196.63	$196.65	$196.60
Purchase #3	$236.34	8.435%	$256.2753	$256.28	$256.30	$256.30
Purchase #4	$185.73	8.389%	$201.3109	$201.31	$201.30	$201.30
Purchase #5	$192.45	6.398%	$204.763	$204.76	$204.75	$204.80
Purchase #6	$88.38	7.536%	$95.0403	$95.04	$95.05	$95.00
Purchase #7	$150.88	7.721%	$162.5294	$162.53	$162.55	$162.50
7 purchase totals =	$1,080.38		$1,172.5381	$1,172.54	$1,172.60	$1,172.50