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	$110.64	13.758%	$125.8619	$125.86	$125.85	$125.90
Purchase #2	$179.75	3.305%	$185.6907	$185.69	$185.70	$185.70
Purchase #3	$31.77	3.772%	$32.9684	$32.97	$32.95	$33.00
Purchase #4	$29.43	6.235%	$31.265	$31.27	$31.25	$31.30
Purchase #5	$104.27	6.762%	$111.3207	$111.32	$111.30	$111.30
Purchase #6	$112.99	13.771%	$128.5499	$128.55	$128.55	$128.50
Purchase #7	$40.72	6.403%	$43.3273	$43.33	$43.35	$43.30
7 purchase totals =	$609.57		$658.9839	$658.99	$658.95	$659.00