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	$111.79	3.390%	$115.5797	$115.58	$115.60	$115.60
Purchase #2	$56.86	4.423%	$59.3749	$59.37	$59.35	$59.40
Purchase #3	$223.73	9.218%	$244.3534	$244.35	$244.35	$244.40
Purchase #4	$6.66	10.233%	$7.3415	$7.34	$7.35	$7.30
Purchase #5	$176.59	13.795%	$200.9506	$200.95	$200.95	$201.00
Purchase #6	$47.76	5.322%	$50.3018	$50.30	$50.30	$50.30
Purchase #7	$213.77	13.508%	$242.6461	$242.65	$242.65	$242.60
7 purchase totals =	$837.16		$920.5480	$920.54	$920.55	$920.60