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	$55.65	7.222%	$59.669	$59.67	$59.65	$59.70
Purchase #2	$114.48	9.560%	$125.4243	$125.42	$125.40	$125.40
Purchase #3	$56.25	12.856%	$63.4815	$63.48	$63.50	$63.50
Purchase #4	$182.28	3.838%	$189.2759	$189.28	$189.30	$189.30
Purchase #5	$40.82	4.259%	$42.5585	$42.56	$42.55	$42.60
Purchase #6	$41.90	11.233%	$46.6066	$46.61	$46.60	$46.60
Purchase #7	$95.95	10.455%	$105.9816	$105.98	$106.00	$106.00
7 purchase totals =	$587.33		$632.9974	$633.00	$633.00	$633.10