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	$54.88	8.102%	$59.3264	$59.33	$59.35	$59.30
Purchase #2	$247.37	4.345%	$258.1182	$258.12	$258.10	$258.10
Purchase #3	$218.27	9.409%	$238.807	$238.81	$238.80	$238.80
Purchase #4	$42.55	11.375%	$47.3901	$47.39	$47.40	$47.40
Purchase #5	$86.71	3.718%	$89.9339	$89.93	$89.95	$89.90
Purchase #6	$30.57	3.667%	$31.691	$31.69	$31.70	$31.70
Purchase #7	$180.46	6.328%	$191.8795	$191.88	$191.90	$191.90
7 purchase totals =	$860.81		$917.1461	$917.15	$917.20	$917.10