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	$46.75	11.102%	$51.9402	$51.94	$51.95	$51.90
Purchase #2	$38.55	9.114%	$42.0634	$42.06	$42.05	$42.10
Purchase #3	$135.57	8.525%	$147.1273	$147.13	$147.15	$147.10
Purchase #4	$101.50	11.229%	$112.8974	$112.90	$112.90	$112.90
Purchase #5	$132.29	6.216%	$140.5131	$140.51	$140.50	$140.50
Purchase #6	$208.81	13.695%	$237.4065	$237.41	$237.40	$237.40
Purchase #7	$155.36	10.468%	$171.6231	$171.62	$171.60	$171.60
7 purchase totals =	$818.83		$903.5710	$903.57	$903.55	$903.50