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	$195.53	12.142%	$219.2713	$219.27	$219.25	$219.30
Purchase #2	$141.28	6.203%	$150.0436	$150.04	$150.05	$150.00
Purchase #3	$48.91	12.230%	$54.8917	$54.89	$54.90	$54.90
Purchase #4	$56.31	11.108%	$62.5649	$62.56	$62.55	$62.60
Purchase #5	$125.44	9.212%	$136.9955	$137.00	$137.00	$137.00
Purchase #6	$100.43	5.161%	$105.6132	$105.61	$105.60	$105.60
Purchase #7	$27.60	12.339%	$31.0056	$31.01	$31.00	$31.00
7 purchase totals =	$695.50		$760.3858	$760.38	$760.35	$760.40