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	$101.58	12.755%	$114.5365	$114.54	$114.55	$114.50
Purchase #2	$166.53	7.396%	$178.8466	$178.85	$178.85	$178.80
Purchase #3	$85.65	8.442%	$92.8806	$92.88	$92.90	$92.90
Purchase #4	$151.67	11.121%	$168.5372	$168.54	$168.55	$168.50
Purchase #5	$39.80	4.181%	$41.464	$41.46	$41.45	$41.50
Purchase #6	$229.83	5.185%	$241.7467	$241.75	$241.75	$241.70
Purchase #7	$198.90	10.264%	$219.3151	$219.32	$219.30	$219.30
7 purchase totals =	$973.96		$1,057.3267	$1,057.34	$1,057.35	$1,057.20