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	$183.76	7.139%	$196.8786	$196.88	$196.90	$196.90
Purchase #2	$42.37	12.236%	$47.5544	$47.55	$47.55	$47.60
Purchase #3	$122.88	13.822%	$139.8645	$139.86	$139.85	$139.90
Purchase #4	$59.57	5.770%	$63.0072	$63.01	$63.00	$63.00
Purchase #5	$27.32	4.460%	$28.5385	$28.54	$28.55	$28.50
Purchase #6	$37.97	13.707%	$43.1745	$43.17	$43.15	$43.20
Purchase #7	$150.89	6.391%	$160.5334	$160.53	$160.55	$160.50
7 purchase totals =	$624.76		$679.5511	$679.54	$679.55	$679.60