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	$178.83	6.840%	$191.062	$191.06	$191.05	$191.10
Purchase #2	$243.69	6.167%	$258.7184	$258.72	$258.70	$258.70
Purchase #3	$51.38	8.651%	$55.8249	$55.82	$55.80	$55.80
Purchase #4	$220.67	8.208%	$238.7826	$238.78	$238.80	$238.80
Purchase #5	$214.47	3.609%	$222.2102	$222.21	$222.20	$222.20
Purchase #6	$171.29	13.338%	$194.1367	$194.14	$194.15	$194.10
Purchase #7	$128.26	11.428%	$142.9176	$142.92	$142.90	$142.90
7 purchase totals =	$1,208.59		$1,303.6524	$1,303.65	$1,303.60	$1,303.60