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	$40.42	8.617%	$43.903	$43.90	$43.90	$43.90
Purchase #2	$171.27	4.628%	$179.1964	$179.20	$179.20	$179.20
Purchase #3	$51.96	3.467%	$53.7615	$53.76	$53.75	$53.80
Purchase #4	$191.62	3.822%	$198.9437	$198.94	$198.95	$198.90
Purchase #5	$69.36	3.858%	$72.0359	$72.04	$72.05	$72.00
Purchase #6	$145.39	13.314%	$164.7472	$164.75	$164.75	$164.70
Purchase #7	$219.79	11.159%	$244.3164	$244.32	$244.30	$244.30
7 purchase totals =	$889.81		$956.9041	$956.91	$956.90	$956.80