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	$213.78	13.227%	$242.0567	$242.06	$242.05	$242.10
Purchase #2	$171.83	10.177%	$189.3171	$189.32	$189.30	$189.30
Purchase #3	$168.36	9.823%	$184.898	$184.90	$184.90	$184.90
Purchase #4	$208.78	7.697%	$224.8498	$224.85	$224.85	$224.80
Purchase #5	$75.52	7.780%	$81.3955	$81.40	$81.40	$81.40
Purchase #6	$82.39	5.190%	$86.666	$86.67	$86.65	$86.70
Purchase #7	$12.88	4.844%	$13.5039	$13.50	$13.50	$13.50
7 purchase totals =	$933.54		$1,022.6870	$1,022.70	$1,022.65	$1,022.70