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	$240.48	6.190%	$255.3657	$255.37	$255.35	$255.40
Purchase #2	$170.90	4.675%	$178.8896	$178.89	$178.90	$178.90
Purchase #3	$206.93	4.735%	$216.7281	$216.73	$216.75	$216.70
Purchase #4	$236.50	10.869%	$262.2052	$262.21	$262.20	$262.20
Purchase #5	$120.55	6.654%	$128.5714	$128.57	$128.55	$128.60
Purchase #6	$133.88	6.529%	$142.621	$142.62	$142.60	$142.60
Purchase #7	$165.48	3.648%	$171.5167	$171.52	$171.50	$171.50
7 purchase totals =	$1,274.72		$1,355.8977	$1,355.91	$1,355.85	$1,355.90