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	$148.44	13.514%	$168.5002	$168.50	$168.50	$168.50
Purchase #2	$245.55	13.741%	$279.291	$279.29	$279.30	$279.30
Purchase #3	$218.29	4.142%	$227.3316	$227.33	$227.35	$227.30
Purchase #4	$210.70	3.399%	$217.8617	$217.86	$217.85	$217.90
Purchase #5	$45.37	9.265%	$49.5735	$49.57	$49.55	$49.60
Purchase #6	$38.84	9.859%	$42.6692	$42.67	$42.65	$42.70
Purchase #7	$57.52	8.438%	$62.3735	$62.37	$62.35	$62.40
7 purchase totals =	$964.71		$1,047.6007	$1,047.59	$1,047.55	$1,047.70