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	$117.79	13.815%	$134.0627	$134.06	$134.05	$134.10
Purchase #2	$142.60	9.745%	$156.4964	$156.50	$156.50	$156.50
Purchase #3	$53.35	5.270%	$56.1615	$56.16	$56.15	$56.20
Purchase #4	$150.52	8.367%	$163.114	$163.11	$163.10	$163.10
Purchase #5	$33.28	6.172%	$35.334	$35.33	$35.35	$35.30
Purchase #6	$131.76	6.701%	$140.5892	$140.59	$140.60	$140.60
Purchase #7	$42.83	8.567%	$46.4992	$46.50	$46.50	$46.50
7 purchase totals =	$672.13		$732.2570	$732.25	$732.25	$732.30