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	$78.55	5.326%	$82.7336	$82.73	$82.75	$82.70
Purchase #2	$5.95	12.783%	$6.7106	$6.71	$6.70	$6.70
Purchase #3	$149.93	8.730%	$163.0189	$163.02	$163.00	$163.00
Purchase #4	$249.37	9.398%	$272.8058	$272.81	$272.80	$272.80
Purchase #5	$101.31	3.772%	$105.1314	$105.13	$105.15	$105.10
Purchase #6	$190.31	3.223%	$196.4437	$196.44	$196.45	$196.40
Purchase #7	$187.81	11.751%	$209.8796	$209.88	$209.90	$209.90
7 purchase totals =	$963.23		$1,036.7236	$1,036.72	$1,036.75	$1,036.60