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	$104.55	4.342%	$109.0896	$109.09	$109.10	$109.10
Purchase #2	$182.87	13.118%	$206.8589	$206.86	$206.85	$206.90
Purchase #3	$37.33	4.814%	$39.1271	$39.13	$39.15	$39.10
Purchase #4	$213.47	4.380%	$222.82	$222.82	$222.80	$222.80
Purchase #5	$226.34	5.719%	$239.2844	$239.28	$239.30	$239.30
Purchase #6	$185.50	7.758%	$199.8911	$199.89	$199.90	$199.90
Purchase #7	$239.74	4.182%	$249.7659	$249.77	$249.75	$249.80
7 purchase totals =	$1,189.80		$1,266.8370	$1,266.84	$1,266.85	$1,266.90