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	$199.80	8.687%	$217.1566	$217.16	$217.15	$217.20
Purchase #2	$92.83	10.846%	$102.8983	$102.90	$102.90	$102.90
Purchase #3	$179.95	10.718%	$199.237	$199.24	$199.25	$199.20
Purchase #4	$203.57	4.857%	$213.4574	$213.46	$213.45	$213.50
Purchase #5	$187.40	5.829%	$198.3235	$198.32	$198.30	$198.30
Purchase #6	$80.50	11.670%	$89.8944	$89.89	$89.90	$89.90
Purchase #7	$236.74	9.779%	$259.8908	$259.89	$259.90	$259.90
7 purchase totals =	$1,180.79		$1,280.8580	$1,280.86	$1,280.85	$1,280.90