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	$75.50	4.445%	$78.856	$78.86	$78.85	$78.90
Purchase #2	$89.70	3.714%	$93.0315	$93.03	$93.05	$93.00
Purchase #3	$176.70	11.441%	$196.9162	$196.92	$196.90	$196.90
Purchase #4	$239.67	8.768%	$260.6843	$260.68	$260.70	$260.70
Purchase #5	$31.50	4.626%	$32.9572	$32.96	$32.95	$33.00
Purchase #6	$92.95	11.376%	$103.524	$103.52	$103.50	$103.50
Purchase #7	$85.50	11.788%	$95.5787	$95.58	$95.60	$95.60
7 purchase totals =	$791.52		$861.5479	$861.55	$861.55	$861.60