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	$200.92	6.376%	$213.7307	$213.73	$213.75	$213.70
Purchase #2	$115.83	6.450%	$123.301	$123.30	$123.30	$123.30
Purchase #3	$158.76	5.818%	$167.9967	$168.00	$168.00	$168.00
Purchase #4	$65.63	6.588%	$69.9537	$69.95	$69.95	$70.00
Purchase #5	$230.54	11.320%	$256.6371	$256.64	$256.65	$256.60
Purchase #6	$74.66	10.291%	$82.3433	$82.34	$82.35	$82.30
Purchase #7	$175.27	4.365%	$182.9205	$182.92	$182.90	$182.90
7 purchase totals =	$1,021.61		$1,096.8830	$1,096.88	$1,096.90	$1,096.80