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	$73.51	6.458%	$78.2573	$78.26	$78.25	$78.30
Purchase #2	$50.42	3.156%	$52.0113	$52.01	$52.00	$52.00
Purchase #3	$31.92	3.715%	$33.1058	$33.11	$33.10	$33.10
Purchase #4	$146.67	8.671%	$159.3878	$159.39	$159.40	$159.40
Purchase #5	$237.57	13.360%	$269.3094	$269.31	$269.30	$269.30
Purchase #6	$223.56	12.660%	$251.8627	$251.86	$251.85	$251.90
Purchase #7	$171.37	10.690%	$189.6895	$189.69	$189.70	$189.70
7 purchase totals =	$935.02		$1,033.6238	$1,033.63	$1,033.60	$1,033.70