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	$180.59	10.473%	$199.5032	$199.50	$199.50	$199.50
Purchase #2	$96.77	13.166%	$109.5107	$109.51	$109.50	$109.50
Purchase #3	$63.62	3.541%	$65.8728	$65.87	$65.85	$65.90
Purchase #4	$76.40	9.826%	$83.9071	$83.91	$83.90	$83.90
Purchase #5	$198.54	9.647%	$217.6932	$217.69	$217.70	$217.70
Purchase #6	$229.92	4.404%	$240.0457	$240.05	$240.05	$240.00
Purchase #7	$205.58	9.654%	$225.4267	$225.43	$225.45	$225.40
7 purchase totals =	$1,051.42		$1,141.9594	$1,141.96	$1,141.95	$1,141.90