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	$72.57	12.874%	$81.9127	$81.91	$81.90	$81.90
Purchase #2	$235.86	4.522%	$246.5256	$246.53	$246.55	$246.50
Purchase #3	$99.32	6.452%	$105.7281	$105.73	$105.75	$105.70
Purchase #4	$232.91	12.297%	$261.5509	$261.55	$261.55	$261.60
Purchase #5	$168.96	7.283%	$181.2654	$181.27	$181.25	$181.30
Purchase #6	$231.92	9.348%	$253.5999	$253.60	$253.60	$253.60
Purchase #7	$31.31	6.800%	$33.4391	$33.44	$33.45	$33.40
7 purchase totals =	$1,072.85		$1,164.0217	$1,164.03	$1,164.05	$1,164.00