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	$73.34	8.578%	$79.6311	$79.63	$79.65	$79.60
Purchase #2	$218.69	7.591%	$235.2908	$235.29	$235.30	$235.30
Purchase #3	$78.67	4.471%	$82.1873	$82.19	$82.20	$82.20
Purchase #4	$164.84	9.556%	$180.5921	$180.59	$180.60	$180.60
Purchase #5	$185.72	5.832%	$196.5512	$196.55	$196.55	$196.60
Purchase #6	$19.94	3.775%	$20.6927	$20.69	$20.70	$20.70
Purchase #7	$52.82	8.751%	$57.4423	$57.44	$57.45	$57.40
7 purchase totals =	$794.02		$852.3875	$852.38	$852.45	$852.40