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	$59.47	3.432%	$61.511	$61.51	$61.50	$61.50
Purchase #2	$179.46	7.738%	$193.3466	$193.35	$193.35	$193.30
Purchase #3	$148.58	9.365%	$162.4945	$162.49	$162.50	$162.50
Purchase #4	$151.48	8.680%	$164.6285	$164.63	$164.65	$164.60
Purchase #5	$80.60	3.637%	$83.5314	$83.53	$83.55	$83.50
Purchase #6	$47.97	13.696%	$54.54	$54.54	$54.55	$54.50
Purchase #7	$27.64	12.690%	$31.1475	$31.15	$31.15	$31.10
7 purchase totals =	$695.20		$751.1995	$751.20	$751.25	$751.00