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	$81.79	4.437%	$85.419	$85.42	$85.40	$85.40
Purchase #2	$203.41	7.596%	$218.861	$218.86	$218.85	$218.90
Purchase #3	$79.35	9.155%	$86.6145	$86.61	$86.60	$86.60
Purchase #4	$169.53	6.224%	$180.0815	$180.08	$180.10	$180.10
Purchase #5	$202.97	6.311%	$215.7794	$215.78	$215.80	$215.80
Purchase #6	$142.37	11.292%	$158.4464	$158.45	$158.45	$158.40
Purchase #7	$165.30	12.735%	$186.351	$186.35	$186.35	$186.40
7 purchase totals =	$1,044.72		$1,131.5528	$1,131.55	$1,131.55	$1,131.60