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	$199.89	8.333%	$216.5468	$216.55	$216.55	$216.50
Purchase #2	$156.66	4.719%	$164.0528	$164.05	$164.05	$164.10
Purchase #3	$153.77	9.484%	$168.3535	$168.35	$168.35	$168.40
Purchase #4	$249.27	5.690%	$263.4535	$263.45	$263.45	$263.50
Purchase #5	$74.71	10.410%	$82.4873	$82.49	$82.50	$82.50
Purchase #6	$140.68	8.289%	$152.341	$152.34	$152.35	$152.30
Purchase #7	$26.39	9.519%	$28.9021	$28.90	$28.90	$28.90
7 purchase totals =	$1,001.37		$1,076.1370	$1,076.13	$1,076.15	$1,076.20