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	$49.92	4.679%	$52.2558	$52.26	$52.25	$52.30
Purchase #2	$170.48	11.639%	$190.3222	$190.32	$190.30	$190.30
Purchase #3	$159.77	6.330%	$169.8834	$169.88	$169.90	$169.90
Purchase #4	$246.92	6.344%	$262.5846	$262.58	$262.60	$262.60
Purchase #5	$90.41	7.861%	$97.5171	$97.52	$97.50	$97.50
Purchase #6	$6.85	6.574%	$7.3003	$7.30	$7.30	$7.30
Purchase #7	$250.54	12.859%	$282.7569	$282.76	$282.75	$282.80
7 purchase totals =	$974.89		$1,062.6203	$1,062.62	$1,062.60	$1,062.70