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	$76.86	7.455%	$82.5899	$82.59	$82.60	$82.60
Purchase #2	$47.25	3.770%	$49.0313	$49.03	$49.05	$49.00
Purchase #3	$210.73	8.379%	$228.3871	$228.39	$228.40	$228.40
Purchase #4	$6.69	10.374%	$7.384	$7.38	$7.40	$7.40
Purchase #5	$93.49	5.257%	$98.4048	$98.40	$98.40	$98.40
Purchase #6	$61.41	7.484%	$66.0059	$66.01	$66.00	$66.00
Purchase #7	$196.58	9.538%	$215.3298	$215.33	$215.35	$215.30
7 purchase totals =	$693.01		$747.1328	$747.13	$747.20	$747.10