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	$158.59	3.777%	$164.5799	$164.58	$164.60	$164.60
Purchase #2	$73.61	9.342%	$80.4866	$80.49	$80.50	$80.50
Purchase #3	$86.77	11.218%	$96.5039	$96.50	$96.50	$96.50
Purchase #4	$244.65	4.789%	$256.3663	$256.37	$256.35	$256.40
Purchase #5	$188.99	4.133%	$196.801	$196.80	$196.80	$196.80
Purchase #6	$100.44	6.302%	$106.7697	$106.77	$106.75	$106.80
Purchase #7	$112.97	10.747%	$125.1109	$125.11	$125.10	$125.10
7 purchase totals =	$966.02		$1,026.6183	$1,026.62	$1,026.60	$1,026.70