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	$154.80	7.848%	$166.9487	$166.95	$166.95	$166.90
Purchase #2	$124.50	5.693%	$131.5878	$131.59	$131.60	$131.60
Purchase #3	$176.75	6.327%	$187.933	$187.93	$187.95	$187.90
Purchase #4	$159.78	3.526%	$165.4138	$165.41	$165.40	$165.40
Purchase #5	$134.35	4.359%	$140.2063	$140.21	$140.20	$140.20
Purchase #6	$93.96	3.867%	$97.5934	$97.59	$97.60	$97.60
Purchase #7	$229.86	10.842%	$254.7814	$254.78	$254.80	$254.80
7 purchase totals =	$1,074.00		$1,144.4644	$1,144.46	$1,144.50	$1,144.40