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	$193.88	9.752%	$212.7872	$212.79	$212.80	$212.80
Purchase #2	$79.78	13.208%	$90.3173	$90.32	$90.30	$90.30
Purchase #3	$201.37	12.176%	$225.8888	$225.89	$225.90	$225.90
Purchase #4	$138.86	12.489%	$156.2022	$156.20	$156.20	$156.20
Purchase #5	$160.72	6.149%	$170.6027	$170.60	$170.60	$170.60
Purchase #6	$218.76	3.519%	$226.4582	$226.46	$226.45	$226.50
Purchase #7	$13.38	5.151%	$14.0692	$14.07	$14.05	$14.10
7 purchase totals =	$1,006.75		$1,096.3256	$1,096.33	$1,096.30	$1,096.40