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	$56.31	10.640%	$62.3014	$62.30	$62.30	$62.30
Purchase #2	$98.86	6.745%	$105.5281	$105.53	$105.55	$105.50
Purchase #3	$126.29	10.108%	$139.0554	$139.06	$139.05	$139.10
Purchase #4	$14.45	6.432%	$15.3794	$15.38	$15.40	$15.40
Purchase #5	$153.98	4.368%	$160.7058	$160.71	$160.70	$160.70
Purchase #6	$95.49	5.227%	$100.4813	$100.48	$100.50	$100.50
Purchase #7	$236.78	3.721%	$245.5906	$245.59	$245.60	$245.60
7 purchase totals =	$782.16		$829.0420	$829.05	$829.10	$829.10