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	$120.40	5.860%	$127.4554	$127.46	$127.45	$127.50
Purchase #2	$209.59	3.125%	$216.1397	$216.14	$216.15	$216.10
Purchase #3	$60.93	13.758%	$69.3127	$69.31	$69.30	$69.30
Purchase #4	$186.86	13.735%	$212.5252	$212.53	$212.55	$212.50
Purchase #5	$58.50	5.260%	$61.5771	$61.58	$61.60	$61.60
Purchase #6	$182.70	4.493%	$190.9087	$190.91	$190.90	$190.90
Purchase #7	$124.62	5.766%	$131.8056	$131.81	$131.80	$131.80
7 purchase totals =	$943.60		$1,009.7244	$1,009.74	$1,009.75	$1,009.70