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	$111.94	3.201%	$115.5232	$115.52	$115.50	$115.50
Purchase #2	$165.65	8.182%	$179.2035	$179.20	$179.20	$179.20
Purchase #3	$36.94	10.591%	$40.8523	$40.85	$40.85	$40.90
Purchase #4	$173.56	3.630%	$179.8602	$179.86	$179.85	$179.90
Purchase #5	$174.28	11.389%	$194.1287	$194.13	$194.15	$194.10
Purchase #6	$152.93	12.187%	$171.5676	$171.57	$171.55	$171.60
Purchase #7	$144.88	12.289%	$162.6843	$162.68	$162.70	$162.70
7 purchase totals =	$960.18		$1,043.8198	$1,043.81	$1,043.80	$1,043.90