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	$202.31	10.136%	$222.8161	$222.82	$222.80	$222.80
Purchase #2	$97.32	7.219%	$104.3455	$104.35	$104.35	$104.30
Purchase #3	$49.42	11.219%	$54.9644	$54.96	$54.95	$55.00
Purchase #4	$152.56	11.847%	$170.6338	$170.63	$170.65	$170.60
Purchase #5	$166.50	8.189%	$180.1347	$180.13	$180.15	$180.10
Purchase #6	$120.44	9.415%	$131.7794	$131.78	$131.80	$131.80
Purchase #7	$135.94	5.722%	$143.7185	$143.72	$143.70	$143.70
7 purchase totals =	$924.49		$1,008.3924	$1,008.39	$1,008.40	$1,008.30