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	$232.58	3.527%	$240.7831	$240.78	$240.80	$240.80
Purchase #2	$120.86	5.457%	$127.4553	$127.46	$127.45	$127.50
Purchase #3	$187.89	4.708%	$196.7359	$196.74	$196.75	$196.70
Purchase #4	$115.38	3.524%	$119.446	$119.45	$119.45	$119.40
Purchase #5	$193.81	8.538%	$210.3575	$210.36	$210.35	$210.40
Purchase #6	$71.73	6.223%	$76.1938	$76.19	$76.20	$76.20
Purchase #7	$114.60	9.570%	$125.5672	$125.57	$125.55	$125.60
7 purchase totals =	$1,036.85		$1,096.5388	$1,096.55	$1,096.55	$1,096.60