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	$40.72	5.500%	$42.9596	$42.96	$42.95	$43.00
Purchase #2	$226.64	8.246%	$245.3287	$245.33	$245.35	$245.30
Purchase #3	$86.48	5.177%	$90.9571	$90.96	$90.95	$91.00
Purchase #4	$244.77	10.867%	$271.3692	$271.37	$271.35	$271.40
Purchase #5	$198.34	4.873%	$208.0051	$208.01	$208.00	$208.00
Purchase #6	$52.81	5.213%	$55.563	$55.56	$55.55	$55.60
Purchase #7	$153.69	7.190%	$164.7403	$164.74	$164.75	$164.70
7 purchase totals =	$1,003.45		$1,078.9230	$1,078.93	$1,078.90	$1,079.00