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	$81.25	10.464%	$89.752	$89.75	$89.75	$89.80
Purchase #2	$73.79	11.570%	$82.3275	$82.33	$82.35	$82.30
Purchase #3	$92.67	6.256%	$98.4674	$98.47	$98.45	$98.50
Purchase #4	$147.52	8.531%	$160.1049	$160.10	$160.10	$160.10
Purchase #5	$186.92	9.862%	$205.3541	$205.35	$205.35	$205.40
Purchase #6	$187.59	6.869%	$200.4756	$200.48	$200.50	$200.50
Purchase #7	$215.54	9.477%	$235.9667	$235.97	$235.95	$236.00
7 purchase totals =	$985.28		$1,072.4482	$1,072.45	$1,072.45	$1,072.60