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	$61.83	12.402%	$69.4982	$69.50	$69.50	$69.50
Purchase #2	$78.60	9.193%	$85.8257	$85.83	$85.85	$85.80
Purchase #3	$30.25	9.119%	$33.0085	$33.01	$33.00	$33.00
Purchase #4	$90.48	7.628%	$97.3818	$97.38	$97.40	$97.40
Purchase #5	$146.39	8.869%	$159.3733	$159.37	$159.35	$159.40
Purchase #6	$38.27	11.526%	$42.681	$42.68	$42.70	$42.70
Purchase #7	$73.51	6.109%	$78.0007	$78.00	$78.00	$78.00
7 purchase totals =	$519.33		$565.7692	$565.77	$565.80	$565.80