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	$94.53	7.558%	$101.6746	$101.67	$101.65	$101.70
Purchase #2	$201.78	10.798%	$223.5682	$223.57	$223.55	$223.60
Purchase #3	$86.33	3.638%	$89.4707	$89.47	$89.45	$89.50
Purchase #4	$36.76	7.343%	$39.4593	$39.46	$39.45	$39.50
Purchase #5	$97.36	10.511%	$107.5935	$107.59	$107.60	$107.60
Purchase #6	$43.87	10.492%	$48.4728	$48.47	$48.45	$48.50
Purchase #7	$25.29	10.432%	$27.9283	$27.93	$27.95	$27.90
7 purchase totals =	$585.92		$638.1674	$638.16	$638.10	$638.30