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	$145.86	13.750%	$165.9158	$165.92	$165.90	$165.90
Purchase #2	$208.46	3.359%	$215.4622	$215.46	$215.45	$215.50
Purchase #3	$236.65	3.356%	$244.592	$244.59	$244.60	$244.60
Purchase #4	$232.69	3.127%	$239.9662	$239.97	$239.95	$240.00
Purchase #5	$190.50	3.362%	$196.9046	$196.90	$196.90	$196.90
Purchase #6	$91.32	10.501%	$100.9095	$100.91	$100.90	$100.90
Purchase #7	$99.41	6.379%	$105.7514	$105.75	$105.75	$105.80
7 purchase totals =	$1,204.89		$1,269.5017	$1,269.50	$1,269.45	$1,269.60