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	$137.42	7.403%	$147.5932	$147.59	$147.60	$147.60
Purchase #2	$28.61	3.365%	$29.5727	$29.57	$29.55	$29.60
Purchase #3	$49.94	5.404%	$52.6388	$52.64	$52.65	$52.60
Purchase #4	$52.44	4.423%	$54.7594	$54.76	$54.75	$54.80
Purchase #5	$72.69	10.835%	$80.566	$80.57	$80.55	$80.60
Purchase #6	$88.64	3.270%	$91.5385	$91.54	$91.55	$91.50
Purchase #7	$203.79	5.653%	$215.3102	$215.31	$215.30	$215.30
7 purchase totals =	$633.53		$671.9788	$671.98	$671.95	$672.00