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	$229.83	6.672%	$245.1643	$245.16	$245.15	$245.20
Purchase #2	$211.64	5.289%	$222.8336	$222.83	$222.85	$222.80
Purchase #3	$84.55	13.758%	$96.1824	$96.18	$96.20	$96.20
Purchase #4	$171.78	4.284%	$179.1391	$179.14	$179.15	$179.10
Purchase #5	$63.59	13.235%	$72.0061	$72.01	$72.00	$72.00
Purchase #6	$200.84	6.582%	$214.0593	$214.06	$214.05	$214.10
Purchase #7	$60.86	10.445%	$67.2168	$67.22	$67.20	$67.20
7 purchase totals =	$1,023.09		$1,096.6016	$1,096.60	$1,096.60	$1,096.60