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	$105.46	7.151%	$113.0014	$113.00	$113.00	$113.00
Purchase #2	$69.64	6.846%	$74.4076	$74.41	$74.40	$74.40
Purchase #3	$100.90	10.705%	$111.7013	$111.70	$111.70	$111.70
Purchase #4	$247.96	10.274%	$273.4354	$273.44	$273.45	$273.40
Purchase #5	$152.85	7.353%	$164.0891	$164.09	$164.10	$164.10
Purchase #6	$241.93	13.792%	$275.297	$275.30	$275.30	$275.30
Purchase #7	$212.36	6.721%	$226.6327	$226.63	$226.65	$226.60
7 purchase totals =	$1,131.10		$1,238.5645	$1,238.57	$1,238.60	$1,238.50