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	$148.47	13.814%	$168.9796	$168.98	$169.00	$169.00
Purchase #2	$121.96	5.431%	$128.5836	$128.58	$128.60	$128.60
Purchase #3	$115.37	9.526%	$126.3601	$126.36	$126.35	$126.40
Purchase #4	$207.78	11.247%	$231.149	$231.15	$231.15	$231.10
Purchase #5	$79.89	12.642%	$89.9897	$89.99	$90.00	$90.00
Purchase #6	$198.36	9.574%	$217.351	$217.35	$217.35	$217.40
Purchase #7	$89.52	12.222%	$100.4611	$100.46	$100.45	$100.50
7 purchase totals =	$961.35		$1,062.8741	$1,062.87	$1,062.90	$1,063.00