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	$159.70	12.508%	$179.6753	$179.68	$179.70	$179.70
Purchase #2	$209.34	3.867%	$217.4352	$217.44	$217.45	$217.40
Purchase #3	$205.82	3.438%	$212.8961	$212.90	$212.90	$212.90
Purchase #4	$124.57	12.779%	$140.4888	$140.49	$140.50	$140.50
Purchase #5	$98.74	12.813%	$111.3916	$111.39	$111.40	$111.40
Purchase #6	$200.46	10.504%	$221.5163	$221.52	$221.50	$221.50
Purchase #7	$148.38	12.452%	$166.8563	$166.86	$166.85	$166.90
7 purchase totals =	$1,147.01		$1,250.2596	$1,250.28	$1,250.30	$1,250.30