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	$87.42	13.210%	$98.9682	$98.97	$98.95	$99.00
Purchase #2	$91.56	8.177%	$99.0469	$99.05	$99.05	$99.00
Purchase #3	$19.55	10.329%	$21.5693	$21.57	$21.55	$21.60
Purchase #4	$13.88	5.120%	$14.5907	$14.59	$14.60	$14.60
Purchase #5	$29.61	9.871%	$32.5328	$32.53	$32.55	$32.50
Purchase #6	$160.60	11.801%	$179.5524	$179.55	$179.55	$179.60
Purchase #7	$5.84	12.311%	$6.559	$6.56	$6.55	$6.60
7 purchase totals =	$408.46		$452.8193	$452.82	$452.80	$452.90