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	$172.89	3.169%	$178.3689	$178.37	$178.35	$178.40
Purchase #2	$196.42	8.215%	$212.5559	$212.56	$212.55	$212.60
Purchase #3	$218.49	8.176%	$236.3537	$236.35	$236.35	$236.40
Purchase #4	$238.91	12.648%	$269.1273	$269.13	$269.15	$269.10
Purchase #5	$191.50	7.841%	$206.5155	$206.52	$206.50	$206.50
Purchase #6	$132.50	8.358%	$143.5744	$143.57	$143.55	$143.60
Purchase #7	$62.67	7.757%	$67.5313	$67.53	$67.55	$67.50
7 purchase totals =	$1,213.38		$1,314.0270	$1,314.03	$1,314.00	$1,314.10